virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:46 -04:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2022-02-16 15:31:36 +11:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:47 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-15 09:46:30 -05:00
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2020-08-19 18:19:46 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2025-07-03 14:47:38 +08:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2021-03-18 08:52:22 -05:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:44 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-15 13:46:22 -04:00
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2024-05-17 21:04:35 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:19 -04:00
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2024-08-25 16:07:16 +03:00
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2020-08-19 18:19:44 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
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2024-08-25 16:07:16 +03:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:46 -04:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2020-08-19 18:19:46 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:18 -04:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:18 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:18 -04:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-04-20 17:01:34 +02:00
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2019-10-15 13:46:26 -04:00
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2024-08-31 17:37:50 +08:00
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2019-10-15 13:46:26 -04:00
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2021-11-25 15:05:25 +08:00
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2020-08-19 18:19:47 -04:00
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2021-11-25 15:05:25 +08:00
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2020-08-19 18:19:47 -04:00
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2021-11-25 15:05:25 +08:00
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2020-08-19 18:19:47 -04:00
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2021-08-04 13:22:58 +02:00
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2020-08-19 18:19:47 -04:00
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2021-08-04 13:22:58 +02:00
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2020-08-19 18:19:47 -04:00
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2021-08-04 13:22:58 +02:00
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2020-08-19 18:19:47 -04:00
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2021-11-25 15:05:25 +08:00
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2020-08-19 18:19:47 -04:00
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2021-08-04 13:22:58 +02:00
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2020-08-19 18:19:47 -04:00
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2021-08-04 13:22:58 +02:00
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2020-08-19 18:19:47 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-15 13:46:25 -04:00
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2019-10-30 11:07:19 -04:00
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2019-10-15 13:46:25 -04:00
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2024-02-12 19:11:48 -05:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
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2024-04-25 06:44:00 -04:00
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2024-02-12 19:11:48 -05:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
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2024-08-25 16:07:16 +03:00
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2024-10-06 21:43:41 +03:00
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2024-08-25 16:07:16 +03:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-25 16:07:15 +03:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-25 16:07:15 +03:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:19 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2024-05-17 21:04:35 +02:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
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|
|
|
2019-10-30 11:07:19 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:19 -04:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-25 16:07:16 +03:00
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2025-10-27 03:46:47 -07:00
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2024-08-25 16:07:16 +03:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2024-02-12 19:11:48 -05:00
|
|
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
|
|
|
|
|
2024-02-12 19:11:48 -05:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
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2024-08-25 16:07:16 +03:00
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2024-02-12 19:11:48 -05:00
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2024-08-25 16:07:16 +03:00
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2024-02-12 19:11:48 -05:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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|
2024-02-12 19:11:49 -05:00
|
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|
|
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|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2024-08-25 16:07:16 +03:00
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|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2026-03-11 22:05:17 +01:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:47 -05:00
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2024-10-06 21:43:24 +03:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-15 13:46:25 -04:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2024-01-15 11:09:14 +08:00
|
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|
2024-05-17 21:04:35 +02:00
|
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|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2019-10-15 13:46:22 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
|
2019-10-15 13:46:22 -04:00
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2024-05-17 21:04:35 +02:00
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2019-10-15 13:46:26 -04:00
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2019-10-15 13:46:22 -04:00
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2019-10-15 13:46:26 -04:00
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2019-10-15 13:46:22 -04:00
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2020-04-20 17:59:34 +02:00
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2019-10-15 13:46:22 -04:00
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2019-10-15 13:46:26 -04:00
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2024-08-31 17:37:50 +08:00
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2019-10-15 13:46:26 -04:00
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2024-08-31 17:37:50 +08:00
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2019-10-15 13:46:26 -04:00
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2024-05-17 21:04:34 +02:00
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2019-10-15 13:46:26 -04:00
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2020-04-20 17:59:34 +02:00
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2019-10-15 13:46:26 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2019-10-30 11:07:17 -04:00
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2019-10-30 11:07:18 -04:00
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2019-10-30 11:07:17 -04:00
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2019-10-30 11:07:18 -04:00
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2019-10-30 11:07:17 -04:00
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2024-05-17 21:04:34 +02:00
|
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2019-10-30 11:07:17 -04:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
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|
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|
|
|
2024-05-17 21:04:35 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2019-10-30 11:07:17 -04:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-31 17:37:50 +08:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-31 17:37:50 +08:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2026-02-16 07:31:58 +00:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-04-20 17:01:34 +02:00
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2024-10-24 10:17:58 -07:00
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2020-04-20 17:01:34 +02:00
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2024-10-24 10:18:09 -07:00
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2020-04-20 17:01:34 +02:00
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2020-04-20 17:59:34 +02:00
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2020-04-20 17:01:34 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-04-20 17:01:34 +02:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2026-02-16 07:31:58 +00:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-01-15 11:09:14 +08:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-04-20 17:01:34 +02:00
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treewide: Replace kmalloc with kmalloc_obj for non-scalar types
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
2026-02-20 23:49:23 -08:00
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2020-04-20 17:01:34 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-05-17 21:04:35 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2025-06-17 15:43:23 +02:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2024-10-06 21:43:41 +03:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2025-06-17 15:43:23 +02:00
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2024-10-06 21:43:41 +03:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2024-10-06 21:43:41 +03:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2025-06-17 15:43:23 +02:00
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2024-10-06 21:43:41 +03:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:44 -04:00
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2021-11-02 11:08:19 +01:00
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2020-08-19 18:19:44 -04:00
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2024-05-17 21:04:35 +02:00
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2020-08-19 18:19:44 -04:00
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2024-05-17 21:04:35 +02:00
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2020-08-19 18:19:44 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-07-08 09:48:10 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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|
virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-05 05:39:36 -04:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-05-01 17:38:16 +02:00
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2020-08-19 18:19:44 -04:00
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2026-02-21 16:37:42 -08:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2026-02-21 16:37:42 -08:00
|
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|
|
virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
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2026-02-21 16:37:42 -08:00
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|
|
2024-07-08 09:48:10 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:44 -04:00
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2024-07-08 09:48:10 +02:00
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2020-08-19 18:19:44 -04:00
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2024-07-08 09:48:10 +02:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:44 -04:00
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2024-07-08 09:48:10 +02:00
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|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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|
2024-07-08 09:48:14 +02:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-07-08 09:48:10 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2022-06-09 22:08:38 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:46 -04:00
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2022-05-13 15:10:58 -07:00
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2025-06-19 18:58:05 +10:00
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2020-08-19 18:19:46 -04:00
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2022-06-22 17:17:58 -04:00
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2020-08-19 18:19:46 -04:00
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2025-09-04 20:01:19 +08:00
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2020-08-19 18:19:46 -04:00
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2022-05-13 15:10:58 -07:00
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2020-08-19 18:19:46 -04:00
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2023-06-15 12:13:25 -06:00
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2020-08-19 18:19:46 -04:00
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2024-02-15 09:46:30 -05:00
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2020-08-19 18:19:46 -04:00
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2024-02-15 09:46:30 -05:00
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2020-08-19 18:19:46 -04:00
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2024-02-15 09:46:30 -05:00
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2020-08-19 18:19:46 -04:00
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2020-10-19 14:28:30 -07:00
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2020-08-19 18:19:46 -04:00
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2020-10-19 14:28:30 -07:00
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2020-08-19 18:19:46 -04:00
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2024-02-15 09:46:30 -05:00
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2020-08-19 18:19:46 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2026-02-21 16:37:42 -08:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2024-02-12 19:11:48 -05:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
|
2020-08-19 18:19:46 -04:00
|
|
|
|
|
|
|
|
|
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|
|
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|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2024-02-12 19:11:48 -05:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2021-10-13 06:55:44 -04:00
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2022-06-09 22:08:38 -04:00
|
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2024-02-12 19:11:48 -05:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-25 16:07:16 +03:00
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2024-02-12 19:11:48 -05:00
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2024-08-25 16:07:16 +03:00
|
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2024-02-12 19:11:48 -05:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2019-10-30 11:07:19 -04:00
|
|
|
|
2021-10-13 06:55:44 -04:00
|
|
|
|
2022-06-09 22:08:38 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
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|
|
2024-08-25 16:07:15 +03:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2019-11-11 20:23:59 +08:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
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|
|
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|
|
|
|
2019-11-11 20:23:59 +08:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2024-05-29 17:09:07 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:18 -04:00
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2024-05-29 17:09:07 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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treewide: Replace kmalloc with kmalloc_obj for non-scalar types
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
2026-02-20 23:49:23 -08:00
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2019-10-30 11:07:18 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:18 -04:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:18 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2019-10-30 11:07:18 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-30 11:07:17 -04:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-05-29 17:09:07 +02:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
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2024-10-24 10:18:09 -07:00
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virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
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2024-10-24 10:18:09 -07:00
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virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
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2024-10-24 10:18:09 -07:00
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virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
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2024-10-24 10:18:09 -07:00
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|
|
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|
|
virtiofs: calculate number of scatter-gather elements accurately
virtiofs currently maps various buffers in scatter gather list and it looks
at number of pages (ap->pages) and assumes that same number of pages will
be used both for input and output (sg_count_fuse_req()), and calculates
total number of scatterlist elements accordingly.
But looks like this assumption is not valid in all the cases. For example,
Cai Qian reported that trinity, triggers warning with virtiofs sometimes.
A closer look revealed that if one calls ioctl(fd, 0x5a004000, buf), it
will trigger following warning.
WARN_ON(out_sgs + in_sgs != total_sgs)
In this case, total_sgs = 8, out_sgs=4, in_sgs=3. Number of pages is 2
(ap->pages), but out_sgs are using both the pages but in_sgs are using
only one page. In this case, fuse_do_ioctl() sets different size values
for input and output.
args->in_args[args->in_numargs - 1].size == 6656
args->out_args[args->out_numargs - 1].size == 4096
So current method of calculating how many scatter-gather list elements
will be used is not accurate. Make calculations more precise by parsing
size and ap->descs.
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/linux-fsdevel/5ea77e9f6cb8c2db43b09fbd4158ab2d8c066a0a.camel@redhat.com/
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 14:53:06 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-10-24 10:18:09 -07:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-10-24 10:18:09 -07:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-10-24 10:18:09 -07:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-31 17:37:50 +08:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2025-07-03 14:47:38 +08:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-15 13:46:24 -04:00
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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treewide: Replace kmalloc with kmalloc_obj for non-scalar types
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
2026-02-20 23:49:23 -08:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-08-31 17:37:50 +08:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2019-10-15 13:46:24 -04:00
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2025-07-03 14:47:38 +08:00
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2019-10-15 13:46:24 -04:00
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2025-07-03 14:47:38 +08:00
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2019-10-15 13:46:24 -04:00
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2019-10-15 13:46:26 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-05-29 17:09:07 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2019-10-15 13:46:22 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2025-09-15 17:24:48 -07:00
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|
2024-05-29 17:09:07 +02:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2024-10-06 21:43:41 +03:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
virtio-fs: add multi-queue support
This commit creates a multi-queue mapping at device bring-up.
The driver first attempts to use the existing MSI-X interrupt
affinities (previously disabled), and if not present, will distribute
the request queues evenly over the CPUs.
If the latter fails as well, all CPUs are mapped to request queue zero.
When a request is handed from FUSE to the virtio-fs device driver, the
driver will use the current CPU to index into the multi-queue mapping
and determine the optimal request queue to use.
We measured the performance of this patch with the fio benchmarking
tool, increasing the number of queues results in a significant speedup
for both read and write operations, demonstrating the effectiveness
of multi-queue support.
Host:
- Dell PowerEdge R760
- CPU: Intel(R) Xeon(R) Gold 6438M, 128 cores
- VM: KVM with 32 cores
Virtio-fs device:
- BlueField-3 DPU
- CPU: ARM Cortex-A78AE, 16 cores
- One thread per queue, each busy polling on one request queue
- Each queue is 1024 descriptors deep
Workload:
- fio, sequential read or write, ioengine=libaio, numjobs=32,
4GiB file per job, iodepth=8, bs=256KiB, runtime=30s
Performance Results:
+===========================+==========+===========+
| Number of queues | Fio read | Fio write |
+===========================+==========+===========+
| 1 request queue (GiB/s) | 6.1 | 4.6 |
+---------------------------+----------+-----------+
| 8 request queues (GiB/s) | 25.8 | 10.3 |
+---------------------------+----------+-----------+
| 16 request queues (GiB/s) | 30.9 | 19.5 |
+---------------------------+----------+-----------+
| 32 request queue (GiB/s) | 33.2 | 22.6 |
+---------------------------+----------+-----------+
| Speedup | 5.5x | 5x |
+---------------=-----------+----------+-----------+
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-05-01 17:38:17 +02:00
|
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|
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|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2019-10-15 13:46:22 -04:00
|
|
|
|
2024-08-31 17:37:50 +08:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2024-05-17 21:04:34 +02:00
|
|
|
|
2019-10-15 13:46:26 -04:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2019-10-15 13:46:22 -04:00
|
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|
2024-05-17 21:04:35 +02:00
|
|
|
|
2019-10-15 13:46:22 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
|
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|
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|
2019-11-11 20:23:59 +08:00
|
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|
|
2024-05-29 17:09:07 +02:00
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
|
|
|
|
|
2020-08-19 18:19:47 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2020-08-19 18:19:47 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2020-05-06 17:44:12 +02:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2020-08-19 18:19:47 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:47 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-05-04 14:33:15 -04:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2021-11-25 15:05:25 +08:00
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2021-02-09 17:47:54 -05:00
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2020-08-19 18:19:47 -04:00
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2021-02-09 17:47:54 -05:00
|
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|
2020-08-19 18:19:47 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-05-06 17:44:12 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2020-05-06 17:44:12 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2020-05-06 17:44:12 +02:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2020-05-06 17:44:12 +02:00
|
|
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|
|
2020-08-19 18:19:56 -04:00
|
|
|
|
|
|
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|
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|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2020-05-06 17:44:12 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2020-05-06 17:44:12 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-05-06 17:44:12 +02:00
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2021-10-21 10:01:38 +02:00
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2020-05-06 17:44:12 +02:00
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2021-10-21 10:01:38 +02:00
|
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2020-05-06 17:44:12 +02:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2020-05-06 17:44:12 +02:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2020-05-06 17:44:12 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2021-03-18 08:52:22 -05:00
|
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|
2020-05-06 17:44:12 +02:00
|
|
|
|
2021-03-18 08:52:22 -05:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2025-04-07 19:50:49 +08:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2021-03-18 08:52:22 -05:00
|
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|
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|
|
2020-11-11 17:22:32 +01:00
|
|
|
|
2026-02-21 16:37:42 -08:00
|
|
|
|
2020-11-11 17:22:32 +01:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2026-02-21 16:37:42 -08:00
|
|
|
|
2020-11-11 17:22:32 +01:00
|
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|
|
2020-05-06 17:44:12 +02:00
|
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|
|
2021-04-14 10:40:58 +02:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-04-21 14:47:15 +02:00
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2021-05-20 17:46:54 +02:00
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virtiofs: use pages instead of pointer for kernel direct IO
When trying to insert a 10MB kernel module kept in a virtio-fs with cache
disabled, the following warning was reported:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 404 at mm/page_alloc.c:4551 ......
Modules linked in:
CPU: 1 PID: 404 Comm: insmod Not tainted 6.9.0-rc5+ #123
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ......
RIP: 0010:__alloc_pages+0x2bf/0x380
......
Call Trace:
<TASK>
? __warn+0x8e/0x150
? __alloc_pages+0x2bf/0x380
__kmalloc_large_node+0x86/0x160
__kmalloc+0x33c/0x480
virtio_fs_enqueue_req+0x240/0x6d0
virtio_fs_wake_pending_and_unlock+0x7f/0x190
queue_request_and_unlock+0x55/0x60
fuse_simple_request+0x152/0x2b0
fuse_direct_io+0x5d2/0x8c0
fuse_file_read_iter+0x121/0x160
__kernel_read+0x151/0x2d0
kernel_read+0x45/0x50
kernel_read_file+0x1a9/0x2a0
init_module_from_file+0x6a/0xe0
idempotent_init_module+0x175/0x230
__x64_sys_finit_module+0x5d/0xb0
x64_sys_call+0x1c3/0x9e0
do_syscall_64+0x3d/0xc0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
......
</TASK>
---[ end trace 0000000000000000 ]---
The warning is triggered as follows:
1) syscall finit_module() handles the module insertion and it invokes
kernel_read_file() to read the content of the module first.
2) kernel_read_file() allocates a 10MB buffer by using vmalloc() and
passes it to kernel_read(). kernel_read() constructs a kvec iter by
using iov_iter_kvec() and passes it to fuse_file_read_iter().
3) virtio-fs disables the cache, so fuse_file_read_iter() invokes
fuse_direct_io(). As for now, the maximal read size for kvec iter is
only limited by fc->max_read. For virtio-fs, max_read is UINT_MAX, so
fuse_direct_io() doesn't split the 10MB buffer. It saves the address and
the size of the 10MB-sized buffer in out_args[0] of a fuse request and
passes the fuse request to virtio_fs_wake_pending_and_unlock().
4) virtio_fs_wake_pending_and_unlock() uses virtio_fs_enqueue_req() to
queue the request. Because virtiofs need DMA-able address, so
virtio_fs_enqueue_req() uses kmalloc() to allocate a bounce buffer for
all fuse args, copies these args into the bounce buffer and passed the
physical address of the bounce buffer to virtiofsd. The total length of
these fuse args for the passed fuse request is about 10MB, so
copy_args_to_argbuf() invokes kmalloc() with a 10MB size parameter and
it triggers the warning in __alloc_pages():
if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp))
return NULL;
5) virtio_fs_enqueue_req() will retry the memory allocation in a
kworker, but it won't help, because kmalloc() will always return NULL
due to the abnormal size and finit_module() will hang forever.
A feasible solution is to limit the value of max_read for virtio-fs, so
the length passed to kmalloc() will be limited. However it will affect
the maximal read size for normal read. And for virtio-fs write initiated
from kernel, it has the similar problem but now there is no way to limit
fc->max_write in kernel.
So instead of limiting both the values of max_read and max_write in
kernel, introducing use_pages_for_kvec_io in fuse_conn and setting it as
true in virtiofs. When use_pages_for_kvec_io is enabled, fuse will use
pages instead of pointer to pass the KVEC_IO data.
After switching to pages for KVEC_IO data, these pages will be used for
DMA through virtio-fs. If these pages are backed by vmalloc(),
{flush|invalidate}_kernel_vmap_range() are necessary to flush or
invalidate the cache before the DMA operation. So add two new fields in
fuse_args_pages to record the base address of vmalloc area and the
condition indicating whether invalidation is needed. Perform the flush
in fuse_get_user_pages() for write operations and the invalidation in
fuse_release_user_pages() for read operations.
It may seem necessary to introduce another field in fuse_conn to
indicate that these KVEC_IO pages are used for DMA, However, considering
that virtio-fs is currently the only user of use_pages_for_kvec_io, just
reuse use_pages_for_kvec_io to indicate that these pages will be used
for DMA.
Fixes: a62a8ef9d97d ("virtio-fs: add virtiofs filesystem")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Tested-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2024-08-31 17:37:49 +08:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2021-03-18 08:52:22 -05:00
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2020-05-06 17:44:12 +02:00
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2020-11-11 17:22:31 +01:00
|
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2021-10-21 10:01:39 +02:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:47 -04:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-11-11 17:22:32 +01:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2021-08-04 13:22:58 +02:00
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2020-08-19 18:19:47 -04:00
|
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|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2020-08-19 18:19:47 -04:00
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2021-06-04 18:11:53 +02:00
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2026-02-21 16:37:42 -08:00
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2020-08-19 18:19:47 -04:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-09-03 17:16:26 +02:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:49 -05:00
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2024-02-12 19:11:48 -05:00
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2024-02-12 19:11:49 -05:00
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2024-02-12 19:11:48 -05:00
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2024-02-27 10:57:56 -05:00
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2024-02-12 19:11:48 -05:00
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virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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2024-02-12 19:11:48 -05:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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2024-02-12 19:11:48 -05:00
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
|
|
|
2024-02-12 19:11:48 -05:00
|
|
|
|
|
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
2024-02-12 19:11:48 -05:00
|
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|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
|
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|
|
|
2024-02-12 19:11:48 -05:00
|
|
|
|
virtio-fs: add virtiofs filesystem
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-06-12 09:41:17 +01:00
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