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| author | Chinwen Chang <chinwen.chang@mediatek.com> | 2020-10-13 16:53:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-10-13 18:38:31 -0700 |
| commit | 07e5bfe651f8595ca6a777d989016aa8d8217924 (patch) | |
| tree | cb396dd8a281765104d8ec0e8c3bd092ad24f276 /include | |
| parent | 4d1e72437b92598fa371120aade3f7805114bb16 (diff) | |
| download | linux-07e5bfe651f8595ca6a777d989016aa8d8217924.tar.bz2 | |
mmap locking API: add mmap_lock_is_contended()
Patch series "Try to release mmap_lock temporarily in smaps_rollup", v4.
Recently, we have observed some janky issues caused by unpleasantly long
contention on mmap_lock which is held by smaps_rollup when probing large
processes. To address the problem, we let smaps_rollup detect if anyone
wants to acquire mmap_lock for write attempts. If yes, just release the
lock temporarily to ease the contention.
smaps_rollup is a procfs interface which allows users to summarize the
process's memory usage without the overhead of seq_* calls. Android uses
it to sample the memory usage of various processes to balance its memory
pool sizes. If no one wants to take the lock for write requests,
smaps_rollup with this patch will behave like the original one.
Although there are on-going mmap_lock optimizations like range-based
locks, the lock applied to smaps_rollup would be the coarse one, which is
hard to avoid the occurrence of aforementioned issues. So the detection
and temporary release for write attempts on mmap_lock in smaps_rollup is
still necessary.
This patch (of 3):
Add new API to query if someone wants to acquire mmap_lock for write
attempts.
Using this instead of rwsem_is_contended makes it more tolerant of future
changes to the lock type.
Signed-off-by: Chinwen Chang <chinwen.chang@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Michel Lespinasse <walken@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Daniel Kiss <daniel.kiss@arm.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jimmy Assarsson <jimmyassarsson@gmail.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/1597715898-3854-1-git-send-email-chinwen.chang@mediatek.com
Link: http://lkml.kernel.org/r/1597715898-3854-2-git-send-email-chinwen.chang@mediatek.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mmap_lock.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index 0707671851a8..18e7eae9b5ba 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -87,4 +87,9 @@ static inline void mmap_assert_write_locked(struct mm_struct *mm) VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); } +static inline int mmap_lock_is_contended(struct mm_struct *mm) +{ + return rwsem_is_contended(&mm->mmap_lock); +} + #endif /* _LINUX_MMAP_LOCK_H */ |