The patch titled
Subject: mmap locking API: add mmap_lock_is_contended()
has been removed from the -mm tree. Its filename was
mmap-locking-api-add-mmap_lock_is_contended.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Chinwen Chang <chinwen.chang@xxxxxxxxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/1597715898-3854-1-git-send-email-chinwen.chang@xxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1597715898-3854-2-git-send-email-chinwen.chang@xxxxxxxxxxxx
Signed-off-by: Chinwen Chang <chinwen.chang@xxxxxxxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Acked-by: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Daniel Kiss <daniel.kiss@xxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Jimmy Assarsson <jimmyassarsson@xxxxxxxxx>
Cc: Laurent Dufour <ldufour@xxxxxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmap_lock.h | 5 +++++
1 file changed, 5 insertions(+)
--- a/include/linux/mmap_lock.h~mmap-locking-api-add-mmap_lock_is_contended
+++ a/include/linux/mmap_lock.h
@@ -87,4 +87,9 @@ static inline void mmap_assert_write_loc
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 */
_
Patches currently in -mm which might be from chinwen.chang@xxxxxxxxxxxx are
