From e66f09725771ac5b1b868d6b19eba84e30ffad88 Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Wed, 11 Sep 2013 14:21:26 -0700 Subject: [PATCH] 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: Joonsoo Kim Acked-by: Johannes Weiner Cc: Minchan Kim Cc: Mel Gorman Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 544d19d..42c5930 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1909,7 +1909,7 @@ zonelist_scan: !cpuset_zone_allowed_softwall(zone, gfp_mask)) continue; 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; /* * Distribute pages in proportion to the individual -- 2.7.4