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authorVlastimil Babka <vbabka@suse.cz>2017-05-09 01:54:33 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-05-09 03:15:09 +0300
commit228d7e33903040a0b9dd9a5ee9b3a49c538c0613 (patch)
tree17eb03bb7f86959fba7506b304e43b3c53ea56c8 /mm
parentf25ba6dccc3bfe7e1524f4498a171be038507c45 (diff)
downloadlinux-228d7e33903040a0b9dd9a5ee9b3a49c538c0613.tar.xz
mm, compaction: remove redundant watermark check in compact_finished()
When detecting whether compaction has succeeded in forming a high-order page, __compact_finished() employs a watermark check, followed by an own search for a suitable page in the freelists. This is not ideal for two reasons: - The watermark check also searches high-order freelists, but has a less strict criteria wrt fallback. It's therefore redundant and waste of cycles. This was different in the past when high-order watermark check attempted to apply reserves to high-order pages. - The watermark check might actually fail due to lack of order-0 pages. Compaction can't help with that, so there's no point in continuing because of that. It's possible that high-order page still exists and it terminates. This patch therefore removes the watermark check. This should save some cycles and terminate compaction sooner in some cases. Link: http://lkml.kernel.org/r/20170307131545.28577-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/compaction.c8
1 files changed, 0 insertions, 8 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 09c5282ebdd2..01b1fb8f6f47 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1280,7 +1280,6 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
const int migratetype)
{
unsigned int order;
- unsigned long watermark;
if (cc->contended || fatal_signal_pending(current))
return COMPACT_CONTENDED;
@@ -1308,13 +1307,6 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
if (is_via_compact_memory(cc->order))
return COMPACT_CONTINUE;
- /* Compaction run is not finished if the watermark is not met */
- watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK];
-
- if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
- cc->alloc_flags))
- return COMPACT_CONTINUE;
-
/* Direct compactor: Is a suitable page free? */
for (order = cc->order; order < MAX_ORDER; order++) {
struct free_area *area = &zone->free_area[order];