Commit e66f0972 authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds
Browse files

mm, page_alloc: add unlikely macro to help compiler optimization



We rarely allocate a page with ALLOC_NO_WATERMARKS and it is used in slow
path.  For helping compiler optimization, add unlikely macro to
ALLOC_NO_WATERMARKS checking.

This patch doesn't have any effect now, because gcc already optimize this
properly.  But we cannot assume that gcc always does right and nobody
re-evaluate if gcc do proper optimization with their change, for example,
it is not optimized properly on v3.10.  So adding compiler hint here is
reasonable.
Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1da6f0e1
...@@ -1909,7 +1909,7 @@ get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order, ...@@ -1909,7 +1909,7 @@ get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order,
!cpuset_zone_allowed_softwall(zone, gfp_mask)) !cpuset_zone_allowed_softwall(zone, gfp_mask))
continue; continue;
BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK); BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
if (alloc_flags & ALLOC_NO_WATERMARKS) if (unlikely(alloc_flags & ALLOC_NO_WATERMARKS))
goto try_this_zone; goto try_this_zone;
/* /*
* Distribute pages in proportion to the individual * Distribute pages in proportion to the individual
......
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