Commit 65bb3719 authored Jun 04, 2014 by Mel Gorman Committed by Linus Torvalds Jun 04, 2014

mm: page_alloc: do not update zlc unless the zlc is active



The zlc is used on NUMA machines to quickly skip over zones that are full.
 However it is always updated, even for the first zone scanned when the
zlc might not even be active.  As it's a write to a bitmap that
potentially bounces cache line it's deceptively expensive and most
machines will not care.  Only update the zlc if it was active.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 0bd62b11

mm/page_alloc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2035,7 +2035,7 @@ try_this_zone:
		if (page)
		break;
		this_zone_full:
		if (IS_ENABLED(CONFIG_NUMA))
		if (IS_ENABLED(CONFIG_NUMA) && zlc_active)
		zlc_mark_zone_full(zonelist, z);
		}

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