linux-kernel - [PATCH 05/12] mm, page_alloc: Remove unecessary recheck of nodemask

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Date:	Mon, 24 Aug 2015 13:09:44 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Michal Hocko <mhocko@...nel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 05/12] mm, page_alloc: Remove unecessary recheck of nodemask

An allocation request will either use the given nodemask or the cpuset
current tasks mems_allowed. A cpuset retry will recheck the callers nodemask
and while it's trivial overhead during an extremely rare operation, also
unnecessary. This patch fixes it.

Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
---
 mm/page_alloc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2c1c3bf54d15..32d1cec124bc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3171,7 +3171,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	gfp_t alloc_mask; /* The gfp_t that was actually used for allocation */
 	struct alloc_context ac = {
 		.high_zoneidx = gfp_zone(gfp_mask),
-		.nodemask = nodemask,
+		.nodemask = nodemask ? : &cpuset_current_mems_allowed,
 		.migratetype = gfpflags_to_migratetype(gfp_mask),
 	};
 
@@ -3206,8 +3206,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 
 	/* The preferred zone is used for statistics later */
 	preferred_zoneref = first_zones_zonelist(ac.zonelist, ac.high_zoneidx,
-				ac.nodemask ? : &cpuset_current_mems_allowed,
-				&ac.preferred_zone);
+				ac.nodemask, &ac.preferred_zone);
 	if (!ac.preferred_zone)
 		goto out;
 	ac.classzone_idx = zonelist_zone_idx(preferred_zoneref);
-- 
2.4.6

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