From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx177.postini.com [74.125.245.177]) by kanga.kvack.org (Postfix) with SMTP id 5C5236B0031 for ; Tue, 6 Aug 2013 04:37:37 -0400 (EDT) From: Joonsoo Kim Subject: [PATCH v2 mmotm 1/3] mm, page_alloc: add unlikely macro to help compiler optimization Date: Tue, 6 Aug 2013 17:37:33 +0900 Message-Id: <1375778255-31398-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Minchan Kim , Johannes Weiner , Mel Gorman , Rik van Riel , Joonsoo Kim 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 Signed-off-by: Joonsoo Kim 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org