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Michal Hocko 46459154f9 mm: kvmalloc: make kmalloc fast path real fast path 
There are users like xfs which need larger allocations with NOFAIL
sementic. They are not using kvmalloc currently because the current
implementation tries too hard to allocate through the kmalloc path
which causes a lot of direct reclaim and compaction and that hurts
performance a lot (see 8dc9384b7d ("xfs: reduce kvmalloc overhead for
CIL shadow buffers") for more details).

kvmalloc does support __GFP_RETRY_MAYFAIL semantic to express that
kmalloc (physically contiguous) allocation is preferred and we should go
more aggressive to make it happen. There is currently no way to express
that kmalloc should be very lightweight and as it has been argued [1]
this mode should be default to support kvmalloc(NOFAIL) with a
lightweight kmalloc path which is currently impossible to express as
__GFP_NOFAIL cannot be combined by any other reclaim modifiers.

This patch makes all kmalloc allocations GFP_NOWAIT unless
__GFP_RETRY_MAYFAIL is provided to kvmalloc. This allows to support both
fail fast and retry hard on physically contiguous memory with vmalloc
fallback.

There is a potential downside that relatively small allocations (smaller
than PAGE_ALLOC_COSTLY_ORDER) could fallback to vmalloc too easily and
cause page block fragmentation. We cannot really rule that out but it
seems that xlog_cil_kvmalloc use doesn't indicate this to be happening.

[1] https://lore.kernel.org/all/Z-3i1wATGh6vI8x8@dread.disaster.area/T/#u

Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Link: https://patch.msgid.link/Z-48K0OdNxZXcnkB@tiehlicka
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
History 2025-04-22 09:37:46 +02:00
arch
block
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto
Documentation
drivers gcc-15: work around sequence-point warning 2025-04-20 11:57:54 -07:00
fs
include
init Kconfig: switch CONFIG_SYSFS_SYCALL default to n 2025-04-15 10:28:35 +02:00
io_uring
ipc
kernel vfs-6.15-rc3.fixes.2 2025-04-19 14:31:08 -07:00
lib
LICENSES
mm
net Including fixes from Bluetooth, CAN and Netfilter. 2025-04-17 11:45:30 -07:00
rust
samples samples/livepatch: add module descriptions 2025-04-11 17:32:38 -07:00
scripts Rust fixes for v6.15 2025-04-19 10:02:43 -07:00
security
sound ASoC: Fixes for v6.15 2025-04-11 15:51:19 +02:00
tools tracing fixes for v6.15 2025-04-19 11:57:36 -07:00
usr
virt ARM: 2025-04-08 13:47:55 -07:00
.clang-format clang-format: Update the ForEachMacros list for v6.15-rc1 2025-04-13 11:03:59 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-01-10 00:17:25 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore
.mailmap
.rustfmt.toml
COPYING
CREDITS MAINTAINERS: update SLAB ALLOCATOR maintainers 2025-04-17 20:10:06 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS 16 hotfixes. 2 are cc:stable and the remainder address post-6.14 issues 2025-04-19 21:46:58 -07:00
Makefile Linux 6.15-rc3 2025-04-20 13:43:47 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.