2019-05-27 08:55:21 +02:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:50 +01:00
|
|
|
|
|
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-03-06 12:13:21 +01:00
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
Currently, enabling CONFIG_STACKDEPOT means its stack_table will be
allocated from memblock, even if stack depot ends up not actually used.
The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit.
This is fine for use-cases such as KASAN which is also a config option
and has overhead on its own. But it's an issue for functionality that
has to be actually enabled on boot (page_owner) or depends on hardware
(GPU drivers) and thus the memory might be wasted. This was raised as
an issue [1] when attempting to add stackdepot support for SLUB's debug
object tracking functionality. It's common to build kernels with
CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or
create only specific kmem caches with debugging for testing purposes.
It would thus be more efficient if stackdepot's table was allocated only
when actually going to be used. This patch thus makes the allocation
(and whole stack_depot_init() call) optional:
- Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
well-defined point of allocation as part of mem_init(). Make
CONFIG_KASAN select this flag.
- Other users have to call stack_depot_init() as part of their own init
when it's determined that stack depot will actually be used. This may
depend on both config and runtime conditions. Convert current users
which are page_owner and several in the DRM subsystem. Same will be
done for SLUB later.
- Because the init might now be called after the boot-time memblock
allocation has given all memory to the buddy allocator, change
stack_depot_init() to allocate stack_table with kvmalloc() when
memblock is no longer available. Also handle allocation failure by
disabling stackdepot (could have theoretically happened even with
memblock allocation previously), and don't unnecessarily align the
memblock allocation to its own size anymore.
[1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20211013073005.11351-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Marco Elver <elver@google.com> # stackdepot
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
From: Colin Ian King <colin.king@canonical.com>
Subject: lib/stackdepot: fix spelling mistake and grammar in pr_err message
There is a spelling mistake of the work allocation so fix this and
re-phrase the message to make it easier to read.
Link: https://lkml.kernel.org/r/20211015104159.11282-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup
On FLATMEM, we call page_ext_init_flatmem_late() just before
kmem_cache_init() which means stack_depot_init() (called by page owner
init) will not recognize properly it should use kvmalloc() and not
memblock_alloc(). memblock_alloc() will also not issue a warning and
return a block memory that can be invalid and cause kernel page fault when
saving stacks, as reported by the kernel test robot [1].
Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so
that slab_is_available() is true during stack_depot_init(). SPARSEMEM
doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(),
but a different page_ext_init() even later in the boot process.
Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue.
While at it, also actually resolve a checkpatch warning in stack_depot_init()
from DRM CI, which was supposed to be in the original patch already.
[1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3
Due to cd06ab2fd48f ("drm/locking: add backtrace for locking contended
locks without backoff") landing recently to -next adding a new stack depot
user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate
call to stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup4
Due to 4e66934eaadc ("lib: add reference counting tracking
infrastructure") landing recently to net-next adding a new stack depot
user in lib/ref_tracker.c we need to add an appropriate call to
stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/45c1b738-1a2f-5b5f-2f6d-86fab206d01c@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Slab <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-21 22:14:27 -08:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:14 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-11-20 18:47:10 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-02-10 22:15:58 +01:00
|
|
|
|
lib/stackdepot: fix first entry having a 0-handle
Patch series "page_owner: print stacks and their outstanding allocations",
v10.
page_owner is a great debug functionality tool that lets us know about all
pages that have been allocated/freed and their specific stacktrace. This
comes very handy when debugging memory leaks, since with some scripting we
can see the outstanding allocations, which might point to a memory leak.
In my experience, that is one of the most useful cases, but it can get
really tedious to screen through all pages and try to reconstruct the
stack <-> allocated/freed relationship, becoming most of the time a
daunting and slow process when we have tons of allocation/free operations.
This patchset aims to ease that by adding a new functionality into
page_owner. This functionality creates a new directory called
'page_owner_stacks' under 'sys/kernel//debug' with a read-only file called
'show_stacks', which prints out all the stacks followed by their
outstanding number of allocations (being that the times the stacktrace has
allocated but not freed yet). This gives us a clear and a quick overview
of stacks <-> allocated/free.
We take advantage of the new refcount_f field that stack_record struct
gained, and increment/decrement the stack refcount on every
__set_page_owner() (alloc operation) and __reset_page_owner (free
operation) call.
Unfortunately, we cannot use the new stackdepot api STACK_DEPOT_FLAG_GET
because it does not fulfill page_owner needs, meaning we would have to
special case things, at which point makes more sense for page_owner to do
its own {dec,inc}rementing of the stacks. E.g: Using
STACK_DEPOT_FLAG_PUT, once the refcount reaches 0, such stack gets
evicted, so page_owner would lose information.
This patchset also creates a new file called 'set_threshold' within
'page_owner_stacks' directory, and by writing a value to it, the stacks
which refcount is below such value will be filtered out.
A PoC can be found below:
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks.txt
# head -40 page_owner_full_stacks.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
page_cache_ra_unbounded+0x96/0x180
filemap_get_pages+0xfd/0x590
filemap_read+0xcc/0x330
blkdev_read_iter+0xb8/0x150
vfs_read+0x285/0x320
ksys_read+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 521
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_write+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 4609
...
...
# echo 5000 > /sys/kernel/debug/page_owner_stacks/set_threshold
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks_5000.txt
# head -40 page_owner_full_stacks_5000.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_pwrite64+0x75/0x90
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 6781
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
pcpu_populate_chunk+0xec/0x350
pcpu_balance_workfn+0x2d1/0x4a0
process_scheduled_works+0x84/0x380
worker_thread+0x12a/0x2a0
kthread+0xe3/0x110
ret_from_fork+0x30/0x50
ret_from_fork_asm+0x1b/0x30
stack_count: 8641
This patch (of 7):
The very first entry of stack_record gets a handle of 0, but this is wrong
because stackdepot treats a 0-handle as a non-valid one. E.g: See the
check in stack_depot_fetch()
Fix this by adding and offset of 1.
This bug has been lurking since the very beginning of stackdepot, but no
one really cared as it seems. Because of that I am not adding a Fixes
tag.
Link: https://lkml.kernel.org/r/20240215215907.20121-1-osalvador@suse.de
Link: https://lkml.kernel.org/r/20240215215907.20121-2-osalvador@suse.de
Co-developed-by: Marco Elver <elver@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-15 22:59:01 +01:00
|
|
|
|
2023-02-10 22:15:58 +01:00
|
|
|
|
lib/stackdepot: fix first entry having a 0-handle
Patch series "page_owner: print stacks and their outstanding allocations",
v10.
page_owner is a great debug functionality tool that lets us know about all
pages that have been allocated/freed and their specific stacktrace. This
comes very handy when debugging memory leaks, since with some scripting we
can see the outstanding allocations, which might point to a memory leak.
In my experience, that is one of the most useful cases, but it can get
really tedious to screen through all pages and try to reconstruct the
stack <-> allocated/freed relationship, becoming most of the time a
daunting and slow process when we have tons of allocation/free operations.
This patchset aims to ease that by adding a new functionality into
page_owner. This functionality creates a new directory called
'page_owner_stacks' under 'sys/kernel//debug' with a read-only file called
'show_stacks', which prints out all the stacks followed by their
outstanding number of allocations (being that the times the stacktrace has
allocated but not freed yet). This gives us a clear and a quick overview
of stacks <-> allocated/free.
We take advantage of the new refcount_f field that stack_record struct
gained, and increment/decrement the stack refcount on every
__set_page_owner() (alloc operation) and __reset_page_owner (free
operation) call.
Unfortunately, we cannot use the new stackdepot api STACK_DEPOT_FLAG_GET
because it does not fulfill page_owner needs, meaning we would have to
special case things, at which point makes more sense for page_owner to do
its own {dec,inc}rementing of the stacks. E.g: Using
STACK_DEPOT_FLAG_PUT, once the refcount reaches 0, such stack gets
evicted, so page_owner would lose information.
This patchset also creates a new file called 'set_threshold' within
'page_owner_stacks' directory, and by writing a value to it, the stacks
which refcount is below such value will be filtered out.
A PoC can be found below:
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks.txt
# head -40 page_owner_full_stacks.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
page_cache_ra_unbounded+0x96/0x180
filemap_get_pages+0xfd/0x590
filemap_read+0xcc/0x330
blkdev_read_iter+0xb8/0x150
vfs_read+0x285/0x320
ksys_read+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 521
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_write+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 4609
...
...
# echo 5000 > /sys/kernel/debug/page_owner_stacks/set_threshold
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks_5000.txt
# head -40 page_owner_full_stacks_5000.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_pwrite64+0x75/0x90
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 6781
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
pcpu_populate_chunk+0xec/0x350
pcpu_balance_workfn+0x2d1/0x4a0
process_scheduled_works+0x84/0x380
worker_thread+0x12a/0x2a0
kthread+0xe3/0x110
ret_from_fork+0x30/0x50
ret_from_fork_asm+0x1b/0x30
stack_count: 8641
This patch (of 7):
The very first entry of stack_record gets a handle of 0, but this is wrong
because stackdepot treats a 0-handle as a non-valid one. E.g: See the
check in stack_depot_fetch()
Fix this by adding and offset of 1.
This bug has been lurking since the very beginning of stackdepot, but no
one really cared as it seems. Because of that I am not adding a Fixes
tag.
Link: https://lkml.kernel.org/r/20240215215907.20121-1-osalvador@suse.de
Link: https://lkml.kernel.org/r/20240215215907.20121-2-osalvador@suse.de
Co-developed-by: Marco Elver <elver@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-15 22:59:01 +01:00
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-02-10 22:15:52 +01:00
|
|
|
|
2023-02-10 22:15:51 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:55 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
2023-02-10 22:15:55 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:55 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:55 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
2023-02-10 22:15:55 +01:00
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
2023-02-10 22:15:58 +01:00
|
|
|
|
2023-11-20 18:47:08 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:52 +01:00
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
lib/stackdepot: print disabled message only if truly disabled
Patch series "stackdepot: allow evicting stack traces", v4.
Currently, the stack depot grows indefinitely until it reaches its
capacity. Once that happens, the stack depot stops saving new stack
traces.
This creates a problem for using the stack depot for in-field testing and
in production.
For such uses, an ideal stack trace storage should:
1. Allow saving fresh stack traces on systems with a large uptime while
limiting the amount of memory used to store the traces;
2. Have a low performance impact.
Implementing #1 in the stack depot is impossible with the current
keep-forever approach. This series targets to address that. Issue #2 is
left to be addressed in a future series.
This series changes the stack depot implementation to allow evicting
unneeded stack traces from the stack depot. The users of the stack depot
can do that via new stack_depot_save_flags(STACK_DEPOT_FLAG_GET) and
stack_depot_put APIs.
Internal changes to the stack depot code include:
1. Storing stack traces in fixed-frame-sized slots (vs precisely-sized
slots in the current implementation); the slot size is controlled via
CONFIG_STACKDEPOT_MAX_FRAMES (default: 64 frames);
2. Keeping available slots in a freelist (vs keeping an offset to the next
free slot);
3. Using a read/write lock for synchronization (vs a lock-free approach
combined with a spinlock).
This series also integrates the eviction functionality into KASAN: the
tag-based modes evict stack traces when the corresponding entry leaves the
stack ring, and Generic KASAN evicts stack traces for objects once those
leave the quarantine.
With KASAN, despite wasting some space on rounding up the size of each
stack record, the total memory consumed by stack depot gets saturated due
to the eviction of irrelevant stack traces from the stack depot.
With the tag-based KASAN modes, the average total amount of memory used
for stack traces becomes ~0.5 MB (with the current default stack ring size
of 32k entries and the default CONFIG_STACKDEPOT_MAX_FRAMES of 64). With
Generic KASAN, the stack traces take up ~1 MB per 1 GB of RAM (as the
quarantine's size depends on the amount of RAM).
However, with KMSAN, the stack depot ends up using ~4x more memory per a
stack trace than before. Thus, for KMSAN, the stack depot capacity is
increased accordingly. KMSAN uses a lot of RAM for shadow memory anyway,
so the increased stack depot memory usage will not make a significant
difference.
Other users of the stack depot do not save stack traces as often as KASAN
and KMSAN. Thus, the increased memory usage is taken as an acceptable
trade-off. In the future, these other users can take advantage of the
eviction API to limit the memory waste.
There is no measurable boot time performance impact of these changes for
KASAN on x86-64. I haven't done any tests for arm64 modes (the stack
depot without performance optimizations is not suitable for intended use
of those anyway), but I expect a similar result. Obtaining and copying
stack trace frames when saving them into stack depot is what takes the
most time.
This series does not yet provide a way to configure the maximum size of
the stack depot externally (e.g. via a command-line parameter). This
will be added in a separate series, possibly together with the performance
improvement changes.
This patch (of 22):
Currently, if stack_depot_disable=off is passed to the kernel command-line
after stack_depot_disable=on, stack depot prints a message that it is
disabled, while it is actually enabled.
Fix this by moving printing the disabled message to
stack_depot_early_init. Place it before the
__stack_depot_early_init_requested check, so that the message is printed
even if early stack depot init has not been requested.
Also drop the stack_table = NULL assignment from disable_stack_depot, as
stack_table is NULL by default.
Link: https://lkml.kernel.org/r/cover.1700502145.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/73a25c5fff29f3357cd7a9330e85e09bc8da2cbe.1700502145.git.andreyknvl@google.com
Fixes: e1fdc403349c ("lib: stackdepot: add support to disable stack depot")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-11-20 18:46:59 +01:00
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
2023-02-10 22:15:52 +01:00
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
2023-02-10 22:15:51 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
2023-02-10 22:15:51 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:51 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:53 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
2023-02-10 22:15:53 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
lib/stackdepot: print disabled message only if truly disabled
Patch series "stackdepot: allow evicting stack traces", v4.
Currently, the stack depot grows indefinitely until it reaches its
capacity. Once that happens, the stack depot stops saving new stack
traces.
This creates a problem for using the stack depot for in-field testing and
in production.
For such uses, an ideal stack trace storage should:
1. Allow saving fresh stack traces on systems with a large uptime while
limiting the amount of memory used to store the traces;
2. Have a low performance impact.
Implementing #1 in the stack depot is impossible with the current
keep-forever approach. This series targets to address that. Issue #2 is
left to be addressed in a future series.
This series changes the stack depot implementation to allow evicting
unneeded stack traces from the stack depot. The users of the stack depot
can do that via new stack_depot_save_flags(STACK_DEPOT_FLAG_GET) and
stack_depot_put APIs.
Internal changes to the stack depot code include:
1. Storing stack traces in fixed-frame-sized slots (vs precisely-sized
slots in the current implementation); the slot size is controlled via
CONFIG_STACKDEPOT_MAX_FRAMES (default: 64 frames);
2. Keeping available slots in a freelist (vs keeping an offset to the next
free slot);
3. Using a read/write lock for synchronization (vs a lock-free approach
combined with a spinlock).
This series also integrates the eviction functionality into KASAN: the
tag-based modes evict stack traces when the corresponding entry leaves the
stack ring, and Generic KASAN evicts stack traces for objects once those
leave the quarantine.
With KASAN, despite wasting some space on rounding up the size of each
stack record, the total memory consumed by stack depot gets saturated due
to the eviction of irrelevant stack traces from the stack depot.
With the tag-based KASAN modes, the average total amount of memory used
for stack traces becomes ~0.5 MB (with the current default stack ring size
of 32k entries and the default CONFIG_STACKDEPOT_MAX_FRAMES of 64). With
Generic KASAN, the stack traces take up ~1 MB per 1 GB of RAM (as the
quarantine's size depends on the amount of RAM).
However, with KMSAN, the stack depot ends up using ~4x more memory per a
stack trace than before. Thus, for KMSAN, the stack depot capacity is
increased accordingly. KMSAN uses a lot of RAM for shadow memory anyway,
so the increased stack depot memory usage will not make a significant
difference.
Other users of the stack depot do not save stack traces as often as KASAN
and KMSAN. Thus, the increased memory usage is taken as an acceptable
trade-off. In the future, these other users can take advantage of the
eviction API to limit the memory waste.
There is no measurable boot time performance impact of these changes for
KASAN on x86-64. I haven't done any tests for arm64 modes (the stack
depot without performance optimizations is not suitable for intended use
of those anyway), but I expect a similar result. Obtaining and copying
stack trace frames when saving them into stack depot is what takes the
most time.
This series does not yet provide a way to configure the maximum size of
the stack depot externally (e.g. via a command-line parameter). This
will be added in a separate series, possibly together with the performance
improvement changes.
This patch (of 22):
Currently, if stack_depot_disable=off is passed to the kernel command-line
after stack_depot_disable=on, stack depot prints a message that it is
disabled, while it is actually enabled.
Fix this by moving printing the disabled message to
stack_depot_early_init. Place it before the
__stack_depot_early_init_requested check, so that the message is printed
even if early stack depot init has not been requested.
Also drop the stack_table = NULL assignment from disable_stack_depot, as
stack_table is NULL by default.
Link: https://lkml.kernel.org/r/cover.1700502145.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/73a25c5fff29f3357cd7a9330e85e09bc8da2cbe.1700502145.git.andreyknvl@google.com
Fixes: e1fdc403349c ("lib: stackdepot: add support to disable stack depot")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-11-20 18:46:59 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:53 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
|
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
lib/stackdepot: print disabled message only if truly disabled
Patch series "stackdepot: allow evicting stack traces", v4.
Currently, the stack depot grows indefinitely until it reaches its
capacity. Once that happens, the stack depot stops saving new stack
traces.
This creates a problem for using the stack depot for in-field testing and
in production.
For such uses, an ideal stack trace storage should:
1. Allow saving fresh stack traces on systems with a large uptime while
limiting the amount of memory used to store the traces;
2. Have a low performance impact.
Implementing #1 in the stack depot is impossible with the current
keep-forever approach. This series targets to address that. Issue #2 is
left to be addressed in a future series.
This series changes the stack depot implementation to allow evicting
unneeded stack traces from the stack depot. The users of the stack depot
can do that via new stack_depot_save_flags(STACK_DEPOT_FLAG_GET) and
stack_depot_put APIs.
Internal changes to the stack depot code include:
1. Storing stack traces in fixed-frame-sized slots (vs precisely-sized
slots in the current implementation); the slot size is controlled via
CONFIG_STACKDEPOT_MAX_FRAMES (default: 64 frames);
2. Keeping available slots in a freelist (vs keeping an offset to the next
free slot);
3. Using a read/write lock for synchronization (vs a lock-free approach
combined with a spinlock).
This series also integrates the eviction functionality into KASAN: the
tag-based modes evict stack traces when the corresponding entry leaves the
stack ring, and Generic KASAN evicts stack traces for objects once those
leave the quarantine.
With KASAN, despite wasting some space on rounding up the size of each
stack record, the total memory consumed by stack depot gets saturated due
to the eviction of irrelevant stack traces from the stack depot.
With the tag-based KASAN modes, the average total amount of memory used
for stack traces becomes ~0.5 MB (with the current default stack ring size
of 32k entries and the default CONFIG_STACKDEPOT_MAX_FRAMES of 64). With
Generic KASAN, the stack traces take up ~1 MB per 1 GB of RAM (as the
quarantine's size depends on the amount of RAM).
However, with KMSAN, the stack depot ends up using ~4x more memory per a
stack trace than before. Thus, for KMSAN, the stack depot capacity is
increased accordingly. KMSAN uses a lot of RAM for shadow memory anyway,
so the increased stack depot memory usage will not make a significant
difference.
Other users of the stack depot do not save stack traces as often as KASAN
and KMSAN. Thus, the increased memory usage is taken as an acceptable
trade-off. In the future, these other users can take advantage of the
eviction API to limit the memory waste.
There is no measurable boot time performance impact of these changes for
KASAN on x86-64. I haven't done any tests for arm64 modes (the stack
depot without performance optimizations is not suitable for intended use
of those anyway), but I expect a similar result. Obtaining and copying
stack trace frames when saving them into stack depot is what takes the
most time.
This series does not yet provide a way to configure the maximum size of
the stack depot externally (e.g. via a command-line parameter). This
will be added in a separate series, possibly together with the performance
improvement changes.
This patch (of 22):
Currently, if stack_depot_disable=off is passed to the kernel command-line
after stack_depot_disable=on, stack depot prints a message that it is
disabled, while it is actually enabled.
Fix this by moving printing the disabled message to
stack_depot_early_init. Place it before the
__stack_depot_early_init_requested check, so that the message is printed
even if early stack depot init has not been requested.
Also drop the stack_table = NULL assignment from disable_stack_depot, as
stack_table is NULL by default.
Link: https://lkml.kernel.org/r/cover.1700502145.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/73a25c5fff29f3357cd7a9330e85e09bc8da2cbe.1700502145.git.andreyknvl@google.com
Fixes: e1fdc403349c ("lib: stackdepot: add support to disable stack depot")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-11-20 18:46:59 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:53 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
2023-02-10 22:15:53 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:53 +01:00
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
|
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
2023-02-10 22:15:50 +01:00
|
|
|
|
2023-02-10 22:15:52 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:53 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
Currently, enabling CONFIG_STACKDEPOT means its stack_table will be
allocated from memblock, even if stack depot ends up not actually used.
The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit.
This is fine for use-cases such as KASAN which is also a config option
and has overhead on its own. But it's an issue for functionality that
has to be actually enabled on boot (page_owner) or depends on hardware
(GPU drivers) and thus the memory might be wasted. This was raised as
an issue [1] when attempting to add stackdepot support for SLUB's debug
object tracking functionality. It's common to build kernels with
CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or
create only specific kmem caches with debugging for testing purposes.
It would thus be more efficient if stackdepot's table was allocated only
when actually going to be used. This patch thus makes the allocation
(and whole stack_depot_init() call) optional:
- Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
well-defined point of allocation as part of mem_init(). Make
CONFIG_KASAN select this flag.
- Other users have to call stack_depot_init() as part of their own init
when it's determined that stack depot will actually be used. This may
depend on both config and runtime conditions. Convert current users
which are page_owner and several in the DRM subsystem. Same will be
done for SLUB later.
- Because the init might now be called after the boot-time memblock
allocation has given all memory to the buddy allocator, change
stack_depot_init() to allocate stack_table with kvmalloc() when
memblock is no longer available. Also handle allocation failure by
disabling stackdepot (could have theoretically happened even with
memblock allocation previously), and don't unnecessarily align the
memblock allocation to its own size anymore.
[1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20211013073005.11351-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Marco Elver <elver@google.com> # stackdepot
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
From: Colin Ian King <colin.king@canonical.com>
Subject: lib/stackdepot: fix spelling mistake and grammar in pr_err message
There is a spelling mistake of the work allocation so fix this and
re-phrase the message to make it easier to read.
Link: https://lkml.kernel.org/r/20211015104159.11282-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup
On FLATMEM, we call page_ext_init_flatmem_late() just before
kmem_cache_init() which means stack_depot_init() (called by page owner
init) will not recognize properly it should use kvmalloc() and not
memblock_alloc(). memblock_alloc() will also not issue a warning and
return a block memory that can be invalid and cause kernel page fault when
saving stacks, as reported by the kernel test robot [1].
Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so
that slab_is_available() is true during stack_depot_init(). SPARSEMEM
doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(),
but a different page_ext_init() even later in the boot process.
Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue.
While at it, also actually resolve a checkpatch warning in stack_depot_init()
from DRM CI, which was supposed to be in the original patch already.
[1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3
Due to cd06ab2fd48f ("drm/locking: add backtrace for locking contended
locks without backoff") landing recently to -next adding a new stack depot
user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate
call to stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup4
Due to 4e66934eaadc ("lib: add reference counting tracking
infrastructure") landing recently to net-next adding a new stack depot
user in lib/ref_tracker.c we need to add an appropriate call to
stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/45c1b738-1a2f-5b5f-2f6d-86fab206d01c@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Slab <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-21 22:14:27 -08:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
Currently, enabling CONFIG_STACKDEPOT means its stack_table will be
allocated from memblock, even if stack depot ends up not actually used.
The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit.
This is fine for use-cases such as KASAN which is also a config option
and has overhead on its own. But it's an issue for functionality that
has to be actually enabled on boot (page_owner) or depends on hardware
(GPU drivers) and thus the memory might be wasted. This was raised as
an issue [1] when attempting to add stackdepot support for SLUB's debug
object tracking functionality. It's common to build kernels with
CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or
create only specific kmem caches with debugging for testing purposes.
It would thus be more efficient if stackdepot's table was allocated only
when actually going to be used. This patch thus makes the allocation
(and whole stack_depot_init() call) optional:
- Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
well-defined point of allocation as part of mem_init(). Make
CONFIG_KASAN select this flag.
- Other users have to call stack_depot_init() as part of their own init
when it's determined that stack depot will actually be used. This may
depend on both config and runtime conditions. Convert current users
which are page_owner and several in the DRM subsystem. Same will be
done for SLUB later.
- Because the init might now be called after the boot-time memblock
allocation has given all memory to the buddy allocator, change
stack_depot_init() to allocate stack_table with kvmalloc() when
memblock is no longer available. Also handle allocation failure by
disabling stackdepot (could have theoretically happened even with
memblock allocation previously), and don't unnecessarily align the
memblock allocation to its own size anymore.
[1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20211013073005.11351-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Marco Elver <elver@google.com> # stackdepot
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
From: Colin Ian King <colin.king@canonical.com>
Subject: lib/stackdepot: fix spelling mistake and grammar in pr_err message
There is a spelling mistake of the work allocation so fix this and
re-phrase the message to make it easier to read.
Link: https://lkml.kernel.org/r/20211015104159.11282-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup
On FLATMEM, we call page_ext_init_flatmem_late() just before
kmem_cache_init() which means stack_depot_init() (called by page owner
init) will not recognize properly it should use kvmalloc() and not
memblock_alloc(). memblock_alloc() will also not issue a warning and
return a block memory that can be invalid and cause kernel page fault when
saving stacks, as reported by the kernel test robot [1].
Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so
that slab_is_available() is true during stack_depot_init(). SPARSEMEM
doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(),
but a different page_ext_init() even later in the boot process.
Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue.
While at it, also actually resolve a checkpatch warning in stack_depot_init()
from DRM CI, which was supposed to be in the original patch already.
[1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3
Due to cd06ab2fd48f ("drm/locking: add backtrace for locking contended
locks without backoff") landing recently to -next adding a new stack depot
user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate
call to stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup4
Due to 4e66934eaadc ("lib: add reference counting tracking
infrastructure") landing recently to net-next adding a new stack depot
user in lib/ref_tracker.c we need to add an appropriate call to
stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/45c1b738-1a2f-5b5f-2f6d-86fab206d01c@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Slab <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-21 22:14:27 -08:00
|
|
|
|
|
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
|
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
2023-02-10 22:15:56 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
|
|
|
|
|
lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
Currently, enabling CONFIG_STACKDEPOT means its stack_table will be
allocated from memblock, even if stack depot ends up not actually used.
The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit.
This is fine for use-cases such as KASAN which is also a config option
and has overhead on its own. But it's an issue for functionality that
has to be actually enabled on boot (page_owner) or depends on hardware
(GPU drivers) and thus the memory might be wasted. This was raised as
an issue [1] when attempting to add stackdepot support for SLUB's debug
object tracking functionality. It's common to build kernels with
CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or
create only specific kmem caches with debugging for testing purposes.
It would thus be more efficient if stackdepot's table was allocated only
when actually going to be used. This patch thus makes the allocation
(and whole stack_depot_init() call) optional:
- Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
well-defined point of allocation as part of mem_init(). Make
CONFIG_KASAN select this flag.
- Other users have to call stack_depot_init() as part of their own init
when it's determined that stack depot will actually be used. This may
depend on both config and runtime conditions. Convert current users
which are page_owner and several in the DRM subsystem. Same will be
done for SLUB later.
- Because the init might now be called after the boot-time memblock
allocation has given all memory to the buddy allocator, change
stack_depot_init() to allocate stack_table with kvmalloc() when
memblock is no longer available. Also handle allocation failure by
disabling stackdepot (could have theoretically happened even with
memblock allocation previously), and don't unnecessarily align the
memblock allocation to its own size anymore.
[1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20211013073005.11351-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Marco Elver <elver@google.com> # stackdepot
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
From: Colin Ian King <colin.king@canonical.com>
Subject: lib/stackdepot: fix spelling mistake and grammar in pr_err message
There is a spelling mistake of the work allocation so fix this and
re-phrase the message to make it easier to read.
Link: https://lkml.kernel.org/r/20211015104159.11282-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup
On FLATMEM, we call page_ext_init_flatmem_late() just before
kmem_cache_init() which means stack_depot_init() (called by page owner
init) will not recognize properly it should use kvmalloc() and not
memblock_alloc(). memblock_alloc() will also not issue a warning and
return a block memory that can be invalid and cause kernel page fault when
saving stacks, as reported by the kernel test robot [1].
Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so
that slab_is_available() is true during stack_depot_init(). SPARSEMEM
doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(),
but a different page_ext_init() even later in the boot process.
Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue.
While at it, also actually resolve a checkpatch warning in stack_depot_init()
from DRM CI, which was supposed to be in the original patch already.
[1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3
Due to cd06ab2fd48f ("drm/locking: add backtrace for locking contended
locks without backoff") landing recently to -next adding a new stack depot
user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate
call to stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup4
Due to 4e66934eaadc ("lib: add reference counting tracking
infrastructure") landing recently to net-next adding a new stack depot
user in lib/ref_tracker.c we need to add an appropriate call to
stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/45c1b738-1a2f-5b5f-2f6d-86fab206d01c@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Slab <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-21 22:14:27 -08:00
|
|
|
|
2023-02-10 22:15:54 +01:00
|
|
|
|
lib/stackdepot: allow requesting early initialization dynamically
In a later patch we want to add stackdepot support for object owner
tracking in slub caches, which is enabled by slub_debug boot parameter.
This creates a bootstrap problem as some caches are created early in
boot when slab_is_available() is false and thus stack_depot_init()
tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are
already beyond memblock_free_all(). Ideally memblock allocation should
fail, yet it succeeds, but later the system crashes, which is a
separately handled issue.
To resolve this boostrap issue in a robust way, this patch adds another
way to request stack_depot_early_init(), which happens at a well-defined
point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT,
code that's e.g. processing boot parameters (which happens early enough)
can call a new function stack_depot_want_early_init(), which sets a flag
that stack_depot_early_init() will check.
In this patch we also convert page_owner to this approach. While it
doesn't have the bootstrap issue as slub, it's also a functionality
enabled by a boot param and can thus request stack_depot_early_init()
with memblock allocation instead of later initialization with
kvmalloc().
As suggested by Mike, make stack_depot_early_init() only attempt
memblock allocation and stack_depot_init() only attempt kvmalloc().
Also change the latter to kvcalloc(). In both cases we can lose the
explicit array zeroing, which the allocations do already.
As suggested by Marco, provide empty implementations of the init
functions for !CONFIG_STACKDEPOT builds to simplify the callers.
[1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
2022-03-02 12:02:22 +01:00
|
|
|
|
2021-02-25 17:21:27 -08:00
|
|
|
|
lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
Currently, enabling CONFIG_STACKDEPOT means its stack_table will be
allocated from memblock, even if stack depot ends up not actually used.
The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit.
This is fine for use-cases such as KASAN which is also a config option
and has overhead on its own. But it's an issue for functionality that
has to be actually enabled on boot (page_owner) or depends on hardware
(GPU drivers) and thus the memory might be wasted. This was raised as
an issue [1] when attempting to add stackdepot support for SLUB's debug
object tracking functionality. It's common to build kernels with
CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or
create only specific kmem caches with debugging for testing purposes.
It would thus be more efficient if stackdepot's table was allocated only
when actually going to be used. This patch thus makes the allocation
(and whole stack_depot_init() call) optional:
- Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
well-defined point of allocation as part of mem_init(). Make
CONFIG_KASAN select this flag.
- Other users have to call stack_depot_init() as part of their own init
when it's determined that stack depot will actually be used. This may
depend on both config and runtime conditions. Convert current users
which are page_owner and several in the DRM subsystem. Same will be
done for SLUB later.
- Because the init might now be called after the boot-time memblock
allocation has given all memory to the buddy allocator, change
stack_depot_init() to allocate stack_table with kvmalloc() when
memblock is no longer available. Also handle allocation failure by
disabling stackdepot (could have theoretically happened even with
memblock allocation previously), and don't unnecessarily align the
memblock allocation to its own size anymore.
[1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20211013073005.11351-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Marco Elver <elver@google.com> # stackdepot
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
From: Colin Ian King <colin.king@canonical.com>
Subject: lib/stackdepot: fix spelling mistake and grammar in pr_err message
There is a spelling mistake of the work allocation so fix this and
re-phrase the message to make it easier to read.
Link: https://lkml.kernel.org/r/20211015104159.11282-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup
On FLATMEM, we call page_ext_init_flatmem_late() just before
kmem_cache_init() which means stack_depot_init() (called by page owner
init) will not recognize properly it should use kvmalloc() and not
memblock_alloc(). memblock_alloc() will also not issue a warning and
return a block memory that can be invalid and cause kernel page fault when
saving stacks, as reported by the kernel test robot [1].
Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so
that slab_is_available() is true during stack_depot_init(). SPARSEMEM
doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(),
but a different page_ext_init() even later in the boot process.
Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue.
While at it, also actually resolve a checkpatch warning in stack_depot_init()
from DRM CI, which was supposed to be in the original patch already.
[1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3
Due to cd06ab2fd48f ("drm/locking: add backtrace for locking contended
locks without backoff") landing recently to -next adding a new stack depot
user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate
call to stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Marco Elver <elver@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup4
Due to 4e66934eaadc ("lib: add reference counting tracking
infrastructure") landing recently to net-next adding a new stack depot
user in lib/ref_tracker.c we need to add an appropriate call to
stack_depot_init() there as well.
Link: https://lkml.kernel.org/r/45c1b738-1a2f-5b5f-2f6d-86fab206d01c@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Slab <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-21 22:14:27 -08:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:07 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:10 +01:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
2023-11-20 18:47:07 +01:00
|
|
|
|
2023-02-10 22:16:02 +01:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-02-10 22:16:00 +01:00
|
|
|
|
2023-02-10 22:16:01 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2024-04-01 17:14:58 -07:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:01 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-11-20 18:47:06 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:06 +01:00
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:06 +01:00
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-11-20 18:47:06 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:06 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:10 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-11-20 18:47:06 +01:00
|
|
|
|
2023-02-10 22:16:01 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:09 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:04 +01:00
|
|
|
|
2023-02-10 22:16:01 +01:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
2023-03-06 12:13:21 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
|
|
|
|
|
2024-04-01 17:14:58 -07:00
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:10 +01:00
|
|
|
|
2024-02-23 17:20:13 +03:00
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
lib/stackdepot: fix first entry having a 0-handle
Patch series "page_owner: print stacks and their outstanding allocations",
v10.
page_owner is a great debug functionality tool that lets us know about all
pages that have been allocated/freed and their specific stacktrace. This
comes very handy when debugging memory leaks, since with some scripting we
can see the outstanding allocations, which might point to a memory leak.
In my experience, that is one of the most useful cases, but it can get
really tedious to screen through all pages and try to reconstruct the
stack <-> allocated/freed relationship, becoming most of the time a
daunting and slow process when we have tons of allocation/free operations.
This patchset aims to ease that by adding a new functionality into
page_owner. This functionality creates a new directory called
'page_owner_stacks' under 'sys/kernel//debug' with a read-only file called
'show_stacks', which prints out all the stacks followed by their
outstanding number of allocations (being that the times the stacktrace has
allocated but not freed yet). This gives us a clear and a quick overview
of stacks <-> allocated/free.
We take advantage of the new refcount_f field that stack_record struct
gained, and increment/decrement the stack refcount on every
__set_page_owner() (alloc operation) and __reset_page_owner (free
operation) call.
Unfortunately, we cannot use the new stackdepot api STACK_DEPOT_FLAG_GET
because it does not fulfill page_owner needs, meaning we would have to
special case things, at which point makes more sense for page_owner to do
its own {dec,inc}rementing of the stacks. E.g: Using
STACK_DEPOT_FLAG_PUT, once the refcount reaches 0, such stack gets
evicted, so page_owner would lose information.
This patchset also creates a new file called 'set_threshold' within
'page_owner_stacks' directory, and by writing a value to it, the stacks
which refcount is below such value will be filtered out.
A PoC can be found below:
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks.txt
# head -40 page_owner_full_stacks.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
page_cache_ra_unbounded+0x96/0x180
filemap_get_pages+0xfd/0x590
filemap_read+0xcc/0x330
blkdev_read_iter+0xb8/0x150
vfs_read+0x285/0x320
ksys_read+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 521
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_write+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 4609
...
...
# echo 5000 > /sys/kernel/debug/page_owner_stacks/set_threshold
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks_5000.txt
# head -40 page_owner_full_stacks_5000.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_pwrite64+0x75/0x90
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 6781
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
pcpu_populate_chunk+0xec/0x350
pcpu_balance_workfn+0x2d1/0x4a0
process_scheduled_works+0x84/0x380
worker_thread+0x12a/0x2a0
kthread+0xe3/0x110
ret_from_fork+0x30/0x50
ret_from_fork_asm+0x1b/0x30
stack_count: 8641
This patch (of 7):
The very first entry of stack_record gets a handle of 0, but this is wrong
because stackdepot treats a 0-handle as a non-valid one. E.g: See the
check in stack_depot_fetch()
Fix this by adding and offset of 1.
This bug has been lurking since the very beginning of stackdepot, but no
one really cared as it seems. Because of that I am not adding a Fixes
tag.
Link: https://lkml.kernel.org/r/20240215215907.20121-1-osalvador@suse.de
Link: https://lkml.kernel.org/r/20240215215907.20121-2-osalvador@suse.de
Co-developed-by: Marco Elver <elver@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-15 22:59:01 +01:00
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
lib/stackdepot: fix first entry having a 0-handle
Patch series "page_owner: print stacks and their outstanding allocations",
v10.
page_owner is a great debug functionality tool that lets us know about all
pages that have been allocated/freed and their specific stacktrace. This
comes very handy when debugging memory leaks, since with some scripting we
can see the outstanding allocations, which might point to a memory leak.
In my experience, that is one of the most useful cases, but it can get
really tedious to screen through all pages and try to reconstruct the
stack <-> allocated/freed relationship, becoming most of the time a
daunting and slow process when we have tons of allocation/free operations.
This patchset aims to ease that by adding a new functionality into
page_owner. This functionality creates a new directory called
'page_owner_stacks' under 'sys/kernel//debug' with a read-only file called
'show_stacks', which prints out all the stacks followed by their
outstanding number of allocations (being that the times the stacktrace has
allocated but not freed yet). This gives us a clear and a quick overview
of stacks <-> allocated/free.
We take advantage of the new refcount_f field that stack_record struct
gained, and increment/decrement the stack refcount on every
__set_page_owner() (alloc operation) and __reset_page_owner (free
operation) call.
Unfortunately, we cannot use the new stackdepot api STACK_DEPOT_FLAG_GET
because it does not fulfill page_owner needs, meaning we would have to
special case things, at which point makes more sense for page_owner to do
its own {dec,inc}rementing of the stacks. E.g: Using
STACK_DEPOT_FLAG_PUT, once the refcount reaches 0, such stack gets
evicted, so page_owner would lose information.
This patchset also creates a new file called 'set_threshold' within
'page_owner_stacks' directory, and by writing a value to it, the stacks
which refcount is below such value will be filtered out.
A PoC can be found below:
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks.txt
# head -40 page_owner_full_stacks.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
page_cache_ra_unbounded+0x96/0x180
filemap_get_pages+0xfd/0x590
filemap_read+0xcc/0x330
blkdev_read_iter+0xb8/0x150
vfs_read+0x285/0x320
ksys_read+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 521
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_write+0xa5/0xe0
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 4609
...
...
# echo 5000 > /sys/kernel/debug/page_owner_stacks/set_threshold
# cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks_5000.txt
# head -40 page_owner_full_stacks_5000.txt
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
alloc_pages_mpol+0x91/0x1f0
folio_alloc+0x14/0x50
filemap_alloc_folio+0xb2/0x100
__filemap_get_folio+0x14a/0x490
ext4_write_begin+0xbd/0x4b0 [ext4]
generic_perform_write+0xc1/0x1e0
ext4_buffered_write_iter+0x68/0xe0 [ext4]
ext4_file_write_iter+0x70/0x740 [ext4]
vfs_write+0x33d/0x420
ksys_pwrite64+0x75/0x90
do_syscall_64+0x80/0x160
entry_SYSCALL_64_after_hwframe+0x6e/0x76
stack_count: 6781
prep_new_page+0xa9/0x120
get_page_from_freelist+0x801/0x2210
__alloc_pages+0x18b/0x350
pcpu_populate_chunk+0xec/0x350
pcpu_balance_workfn+0x2d1/0x4a0
process_scheduled_works+0x84/0x380
worker_thread+0x12a/0x2a0
kthread+0xe3/0x110
ret_from_fork+0x30/0x50
ret_from_fork_asm+0x1b/0x30
stack_count: 8641
This patch (of 7):
The very first entry of stack_record gets a handle of 0, but this is wrong
because stackdepot treats a 0-handle as a non-valid one. E.g: See the
check in stack_depot_fetch()
Fix this by adding and offset of 1.
This bug has been lurking since the very beginning of stackdepot, but no
one really cared as it seems. Because of that I am not adding a Fixes
tag.
Link: https://lkml.kernel.org/r/20240215215907.20121-1-osalvador@suse.de
Link: https://lkml.kernel.org/r/20240215215907.20121-2-osalvador@suse.de
Co-developed-by: Marco Elver <elver@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-15 22:59:01 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:15 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:15 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
|
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:15 +01:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2020-12-15 20:43:10 -08:00
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2018-02-06 15:38:24 -08:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:10 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:13 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-11-20 18:47:11 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:01 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:13 +01:00
|
|
|
|
2019-04-25 11:44:56 +02:00
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-11-20 18:47:13 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2022-01-21 22:14:31 -08:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
2022-01-21 22:14:31 -08:00
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2022-01-21 22:14:31 -08:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:52 +01:00
|
|
|
|
2023-11-20 18:47:01 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2019-04-25 11:44:56 +02:00
|
|
|
|
lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizing
As Linus explained [1], setting the stackdepot hash table size as a config
option is suboptimal, especially as stackdepot becomes a dependency of
less "expert" subsystems than initially (e.g. DRM, networking,
SLUB_DEBUG):
: (a) it introduces a new compile-time question that isn't sane to ask
: a regular user, but is now exposed to regular users.
: (b) this by default uses 1MB of memory for a feature that didn't in
: the past, so now if you have small machines you need to make sure you
: make a special kernel config for them.
Ideally we would employ rhashtable for fully automatic resizing, which
should be feasible for many of the new users, but problematic for the
original users with restricted context that call __stack_depot_save() with
can_alloc == false, i.e. KASAN.
However we can easily remove the config option and scale the hash table
automatically with system memory. The STACK_HASH_MASK constant becomes
stack_hash_mask variable and is used only in one mask operation, so the
overhead should be negligible to none. For early allocation we can employ
the existing alloc_large_system_hash() function and perform similar
scaling for the late allocation.
The existing limits of the config option (between 4k and 1M buckets) are
preserved, and scaling factor is set to one bucket per 16kB memory so on
64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while
a 1GB system will use 512kB.
Because KASAN is reported to need the maximum number of buckets even with
smaller amounts of memory [2], set it as such when kasan_enabled().
If needed, the automatic scaling could be complemented with a boot-time
kernel parameter, but it feels pointless to add it without a specific use
case.
[1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/
[2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-20 17:02:49 +02:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:10 +01:00
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-07-28 15:49:10 -07:00
|
|
|
|
2023-02-10 22:15:58 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-12-19 22:19:50 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
2024-01-29 11:07:01 +01:00
|
|
|
|
2021-11-05 13:35:36 -07:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-12-19 22:19:50 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:05 +01:00
|
|
|
|
2023-02-10 22:15:58 +01:00
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:01 +01:00
|
|
|
|
|
|
|
|
|
2016-03-25 14:22:08 -07:00
|
|
|
|
2023-11-20 18:47:13 +01:00
|
|
|
|
2021-11-05 13:35:39 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:13 +01:00
|
|
|
|
|
|
|
|
|
2021-11-05 13:35:39 -07:00
|
|
|
|
2019-04-25 11:44:56 +02:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
mm,page_owner: maintain own list of stack_records structs
page_owner needs to increment a stack_record refcount when a new
allocation occurs, and decrement it on a free operation. In order to do
that, we need to have a way to get a stack_record from a handle.
Implement __stack_depot_get_stack_record() which just does that, and make
it public so page_owner can use it.
Also, traversing all stackdepot buckets comes with its own complexity,
plus we would have to implement a way to mark only those stack_records
that were originated from page_owner, as those are the ones we are
interested in. For that reason, page_owner maintains its own list of
stack_records, because traversing that list is faster than traversing all
buckets while keeping at the same time a low complexity.
For now, add to stack_list only the stack_records of dummy_handle and
failure_handle, and set their refcount of 1.
Further patches will add code to increment or decrement stack_records
count on allocation and free operation.
Link: https://lkml.kernel.org/r/20240215215907.20121-4-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Marco Elver <elver@google.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-15 22:59:03 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-03-06 12:13:21 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:00 +01:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:03 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:10 +01:00
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:15 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-11-20 18:47:15 +01:00
|
|
|
|
stackdepot: make fast paths lock-less again
With the introduction of the pool_rwlock (reader-writer lock), several
fast paths end up taking the pool_rwlock as readers. Furthermore,
stack_depot_put() unconditionally takes the pool_rwlock as a writer.
Despite allowing readers to make forward-progress concurrently,
reader-writer locks have inherent cache contention issues, which does not
scale well on systems with large CPU counts.
Rework the synchronization story of stack depot to again avoid taking any
locks in the fast paths. This is done by relying on RCU-protected list
traversal, and the NMI-safe subset of RCU to delay reuse of freed stack
records. See code comments for more details.
Along with the performance issues, this also fixes incorrect nesting of
rwlock within a raw_spinlock, given that stack depot should still be
usable from anywhere:
| [ BUG: Invalid wait context ]
| -----------------------------
| swapper/0/1 is trying to lock:
| ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags
| other info that might help us debug this:
| context-{5:5}
| 2 locks held by swapper/0/1:
| #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work
| #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock
Stack depot usage stats are similar to the previous version after a KASAN
kernel boot:
$ cat /sys/kernel/debug/stackdepot/stats
pools: 838
allocations: 29865
frees: 6604
in_use: 23261
freelist_size: 1879
The number of pools is the same as previously. The freelist size is
minimally larger, but this may also be due to variance across system
boots. This shows that even though we do not eagerly wait for the next
RCU grace period (such as with synchronize_rcu() or call_rcu()) after
freeing a stack record - requiring depot_pop_free() to "poll" if an entry
may be used - new allocations are very likely to happen in later RCU grace
periods.
Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com
Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces")
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-18 12:01:30 +01:00
|
|
|
|
2023-11-20 18:47:15 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:16:03 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2023-02-10 22:15:49 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2024-01-18 12:01:29 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
