The patch titled
Subject: mm, compaction: remove redundant watermark check in compact_finished()
has been added to the -mm tree. Its filename is
mm-compaction-remove-redundant-watermark-check-in-compact_finished.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-remove-redundant-watermark-check-in-compact_finished.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-remove-redundant-watermark-check-in-compact_finished.patch
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From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: 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@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 8 --------
1 file changed, 8 deletions(-)
diff -puN mm/compaction.c~mm-compaction-remove-redundant-watermark-check-in-compact_finished mm/compaction.c
--- a/mm/compaction.c~mm-compaction-remove-redundant-watermark-check-in-compact_finished
+++ a/mm/compaction.c
@@ -1280,7 +1280,6 @@ static enum compact_result __compact_fin
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_fin
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];
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-compaction-reorder-fields-in-struct-compact_control.patch
mm-compaction-remove-redundant-watermark-check-in-compact_finished.patch
mm-page_alloc-split-smallest-stolen-page-in-fallback.patch
mm-page_alloc-count-movable-pages-when-stealing-from-pageblock.patch
mm-compaction-change-migrate_async_suitable-to-suitable_migration_source.patch
mm-compaction-add-migratetype-to-compact_control.patch
mm-compaction-restrict-async-compaction-to-pageblocks-of-same-migratetype.patch
mm-compaction-finish-whole-pageblock-to-reduce-fragmentation.patch
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