Commit 52e9f87a authored Jul 28, 2016 by Mel Gorman Committed by Linus Torvalds Jul 28, 2016

mm, page_alloc: wake kswapd based on the highest eligible zone

The ac_classzone_idx is used as the basis for waking kswapd and that is
based on the preferred zoneref.  If the preferred zoneref's first zone
is lower than what is available on other nodes, it's possible that
kswapd is woken on a zone with only higher, but still eligible, zones.
As classzone_idx is strictly adhered to now, it causes a problem because
eligible pages are skipped.

For example, node 0 has only DMA32 and node 1 has only NORMAL.  An
allocating context running on node 0 may wake kswapd on node 1 telling
it to skip all NORMAL pages.

Link: http://lkml.kernel.org/r/1467970510-21195-23-git-send-email-mgorman@techsingularity.net


Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e1a55637

mm/page_alloc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -3372,7 +3372,7 @@ static void wake_all_kswapds(unsigned int order, const struct alloc_context *ac)
		for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
		ac->high_zoneidx, ac->nodemask) {
		if (last_pgdat != zone->zone_pgdat)
		wakeup_kswapd(zone, order, ac_classzone_idx(ac));
		wakeup_kswapd(zone, order, ac->high_zoneidx);
		last_pgdat = zone->zone_pgdat;
		}
		}

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