diff options
| author | Waiman Long <Waiman.Long@hp.com> | 2014-08-06 16:05:38 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-06 18:01:17 -0700 |
| commit | 3a79d52aa3c63c939f5a1f86e80e634f84e987c4 (patch) | |
| tree | ea352191eb8bc6afbc98ac3b54d573c1db615c78 /mm | |
| parent | f8303c2582b889351e261ff18c4d8eb197a77db2 (diff) | |
mm, thp: replace smp_mb after atomic_add by smp_mb__after_atomic
In some architectures like x86, atomic_add() is a full memory barrier.
In that case, an additional smp_mb() is just a waste of time. This
patch replaces that smp_mb() by smp_mb__after_atomic() which will avoid
the redundant memory barrier in some architectures.
With a 3.16-rc1 based kernel, this patch reduced the execution time of
breaking 1000 transparent huge pages from 38,245us to 30,964us. A
reduction of 19% which is quite sizeable. It also reduces the %cpu time
of the __split_huge_page_refcount function in the perf profile from
2.18% to 1.15%.
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/huge_memory.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2161490526f0..4b95ff4120f5 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1681,7 +1681,7 @@ static void __split_huge_page_refcount(struct page *page, &page_tail->_count); /* after clearing PageTail the gup refcount can be released */ - smp_mb(); + smp_mb__after_atomic(); /* * retain hwpoison flag of the poisoned tail page: |