linux-kernel - [PATCH 3/7] mm: page_alloc: Use zone node IDs to approximate locality

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Date:	Fri, 13 Dec 2013 14:10:03 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 3/7] mm: page_alloc: Use zone node IDs to approximate locality

zone_local is using node_distance which is a more expensive call than
necessary. On x86, it's another function call in the allocator fast path
and increases cache footprint. This patch makes the assumption zones on a
local node will share the same node ID. The necessary information should
already be cache hot.

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 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 64020eb..fd9677e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1816,7 +1816,7 @@ static void zlc_clear_zones_full(struct zonelist *zonelist)
 
 static bool zone_local(struct zone *local_zone, struct zone *zone)
 {
-	return node_distance(local_zone->node, zone->node) == LOCAL_DISTANCE;
+	return zone_to_nid(zone) == numa_node_id();
 }
 
 static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
-- 
1.8.4

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