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. Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f5c549c..04bec49 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1901,7 +1901,7 @@ 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 -- 1.7.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>