diff options
author | Ingo Molnar <mingo@kernel.org> | 2012-12-02 14:56:50 -0500 |
---|---|---|
committer | Mel Gorman <mgorman@suse.de> | 2012-12-11 09:43:00 -0500 |
commit | 4fc3f1d66b1ef0d7b8dc11f4ff1cc510f78b37d6 (patch) | |
tree | 90baaa56f6b5244525c7637a14550f830486112a /mm/migrate.c | |
parent | 5a505085f043e8380f83610f79642853c051e2f1 (diff) |
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 <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Turner <pjt@google.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Diffstat (limited to 'mm/migrate.c')
-rw-r--r-- | mm/migrate.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index f24e9cc49cc4..6e46485f014c 100644 --- a/mm/migrate.c +++ b/mm/migrate.c | |||
@@ -754,7 +754,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage, | |||
754 | */ | 754 | */ |
755 | if (PageAnon(page)) { | 755 | if (PageAnon(page)) { |
756 | /* | 756 | /* |
757 | * Only page_lock_anon_vma() understands the subtleties of | 757 | * Only page_lock_anon_vma_read() understands the subtleties of |
758 | * getting a hold on an anon_vma from outside one of its mms. | 758 | * getting a hold on an anon_vma from outside one of its mms. |
759 | */ | 759 | */ |
760 | anon_vma = page_get_anon_vma(page); | 760 | anon_vma = page_get_anon_vma(page); |