linux-kernel - [PATCH] mm, page_alloc: don't check cpuset allowed twice in fast-path

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Date:   Fri,  6 Jan 2017 09:18:05 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH] mm, page_alloc: don't check cpuset allowed twice in fast-path

Since commit 682a3385e773 ("mm, page_alloc: inline the fast path of the
zonelist iterator") we replace a NULL nodemask with cpuset_current_mems_allowed
in the fast path, so that get_page_from_freelist() filters nodes allowed by the
cpuset via for_next_zone_zonelist_nodemask(). In that case it's pointless to
also check __cpuset_zone_allowed(), which we can avoid by not using
ALLOC_CPUSET in that scenario.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/page_alloc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2c6d5f64feca..3d86fbe2f4f4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3754,9 +3754,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 
 	if (cpusets_enabled()) {
 		alloc_mask |= __GFP_HARDWALL;
-		alloc_flags |= ALLOC_CPUSET;
 		if (!ac.nodemask)
 			ac.nodemask = &cpuset_current_mems_allowed;
+		else
+			alloc_flags |= ALLOC_CPUSET;
 	}
 
 	gfp_mask &= gfp_allowed_mask;
-- 
2.11.0