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07e5bfe651
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>
95 lines
2 KiB
C
95 lines
2 KiB
C
#ifndef _LINUX_MMAP_LOCK_H
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#define _LINUX_MMAP_LOCK_H
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#include <linux/mmdebug.h>
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#define MMAP_LOCK_INITIALIZER(name) \
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.mmap_lock = __RWSEM_INITIALIZER((name).mmap_lock),
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static inline void mmap_init_lock(struct mm_struct *mm)
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{
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init_rwsem(&mm->mmap_lock);
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}
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static inline void mmap_write_lock(struct mm_struct *mm)
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{
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down_write(&mm->mmap_lock);
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}
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static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass)
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{
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down_write_nested(&mm->mmap_lock, subclass);
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}
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static inline int mmap_write_lock_killable(struct mm_struct *mm)
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{
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return down_write_killable(&mm->mmap_lock);
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}
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static inline bool mmap_write_trylock(struct mm_struct *mm)
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{
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return down_write_trylock(&mm->mmap_lock) != 0;
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}
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static inline void mmap_write_unlock(struct mm_struct *mm)
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{
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up_write(&mm->mmap_lock);
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}
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static inline void mmap_write_downgrade(struct mm_struct *mm)
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{
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downgrade_write(&mm->mmap_lock);
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}
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static inline void mmap_read_lock(struct mm_struct *mm)
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{
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down_read(&mm->mmap_lock);
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}
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static inline int mmap_read_lock_killable(struct mm_struct *mm)
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{
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return down_read_killable(&mm->mmap_lock);
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}
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static inline bool mmap_read_trylock(struct mm_struct *mm)
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{
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return down_read_trylock(&mm->mmap_lock) != 0;
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}
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static inline void mmap_read_unlock(struct mm_struct *mm)
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{
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up_read(&mm->mmap_lock);
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}
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static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
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{
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if (down_read_trylock(&mm->mmap_lock)) {
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rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_);
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return true;
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}
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return false;
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}
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static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
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{
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up_read_non_owner(&mm->mmap_lock);
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}
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static inline void mmap_assert_locked(struct mm_struct *mm)
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{
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lockdep_assert_held(&mm->mmap_lock);
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VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
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}
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static inline void mmap_assert_write_locked(struct mm_struct *mm)
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{
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lockdep_assert_held_write(&mm->mmap_lock);
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VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
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}
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static inline int mmap_lock_is_contended(struct mm_struct *mm)
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{
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return rwsem_is_contended(&mm->mmap_lock);
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}
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#endif /* _LINUX_MMAP_LOCK_H */
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