Commit 372549c2 authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds

mm/compaction: fix wrong order check in compact_finished()

What we want to check here is whether there is highorder freepage in buddy
list of other migratetype in order to steal it without fragmentation.
But, current code just checks cc->order which means allocation request
order.  So, this is wrong.

Without this fix, non-movable synchronous compaction below pageblock order
would not stopped until compaction is complete, because migratetype of
most pageblocks are movable and high order freepage made by compaction is
usually on movable type buddy list.

There is some report related to this bug. See below link.

  http://www.spinics.net/lists/linux-mm/msg81666.html

Although the issued system still has load spike comes from compaction,
this makes that system completely stable and responsive according to his
report.

stress-highalloc test in mmtests with non movable order 7 allocation
doesn't show any notable difference in allocation success rate, but, it
shows more compaction success rate.

Compaction success rate (Compaction success * 100 / Compaction stalls, %)
18.47 : 28.94

Fixes: 1fb3f8ca ("mm: compaction: capture a suitable high-order page immediately when it is made available")
Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>	[3.7+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d6e0b7fa
...@@ -1173,7 +1173,7 @@ static int __compact_finished(struct zone *zone, struct compact_control *cc, ...@@ -1173,7 +1173,7 @@ static int __compact_finished(struct zone *zone, struct compact_control *cc,
return COMPACT_PARTIAL; return COMPACT_PARTIAL;
/* Job done if allocation would set block type */ /* Job done if allocation would set block type */
if (cc->order >= pageblock_order && area->nr_free) if (order >= pageblock_order && area->nr_free)
return COMPACT_PARTIAL; return COMPACT_PARTIAL;
} }
......
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