From 4fc3f1d66b1ef0d7b8dc11f4ff1cc510f78b37d6 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sun, 2 Dec 2012 19:56:50 +0000 Subject: mm/rmap, migration: Make rmap_walk_anon() and try_to_unmap_anon() more scalable rmap_walk_anon() and try_to_unmap_anon() appears to be too careful about locking the anon vma: while it needs protection against anon vma list modifications, it does not need exclusive access to the list itself. Transforming this exclusive lock to a read-locked rwsem removes a global lock from the hot path of page-migration intense threaded workloads which can cause pathological performance like this: 96.43% process 0 [kernel.kallsyms] [k] perf_trace_sched_switch | --- perf_trace_sched_switch __schedule schedule schedule_preempt_disabled __mutex_lock_common.isra.6 __mutex_lock_slowpath mutex_lock | |--50.61%-- rmap_walk | move_to_new_page | migrate_pages | migrate_misplaced_page | __do_numa_page.isra.69 | handle_pte_fault | handle_mm_fault | __do_page_fault | do_page_fault | page_fault | __memset_sse2 | | | --100.00%-- worker_thread | | | --100.00%-- start_thread | --49.39%-- page_lock_anon_vma try_to_unmap_anon try_to_unmap migrate_pages migrate_misplaced_page __do_numa_page.isra.69 handle_pte_fault handle_mm_fault __do_page_fault do_page_fault page_fault __memset_sse2 | --100.00%-- worker_thread start_thread With this change applied the profile is now nicely flat and there's no anon-vma related scheduling/blocking. Rename anon_vma_[un]lock() => anon_vma_[un]lock_write(), to make it clearer that it's an exclusive write-lock in that case - suggested by Rik van Riel. Suggested-by: Linus Torvalds Cc: Peter Zijlstra Cc: Paul Turner Cc: Lee Schermerhorn Cc: Christoph Lameter Cc: Rik van Riel Cc: Mel Gorman Cc: Andrea Arcangeli Cc: Johannes Weiner Cc: Hugh Dickins Signed-off-by: Ingo Molnar Signed-off-by: Mel Gorman --- include/linux/rmap.h | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) (limited to 'include/linux/rmap.h') diff --git a/include/linux/rmap.h b/include/linux/rmap.h index f3f41d242e2..c20635c527a 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -118,7 +118,7 @@ static inline void vma_unlock_anon_vma(struct vm_area_struct *vma) up_write(&anon_vma->root->rwsem); } -static inline void anon_vma_lock(struct anon_vma *anon_vma) +static inline void anon_vma_lock_write(struct anon_vma *anon_vma) { down_write(&anon_vma->root->rwsem); } @@ -128,6 +128,17 @@ static inline void anon_vma_unlock(struct anon_vma *anon_vma) up_write(&anon_vma->root->rwsem); } +static inline void anon_vma_lock_read(struct anon_vma *anon_vma) +{ + down_read(&anon_vma->root->rwsem); +} + +static inline void anon_vma_unlock_read(struct anon_vma *anon_vma) +{ + up_read(&anon_vma->root->rwsem); +} + + /* * anon_vma helper functions. */ @@ -220,8 +231,8 @@ int try_to_munlock(struct page *); /* * Called by memory-failure.c to kill processes. */ -struct anon_vma *page_lock_anon_vma(struct page *page); -void page_unlock_anon_vma(struct anon_vma *anon_vma); +struct anon_vma *page_lock_anon_vma_read(struct page *page); +void page_unlock_anon_vma_read(struct anon_vma *anon_vma); int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma); /* -- cgit v1.2.3-70-g09d2