The patch titled
Subject: mm, compaction: use correct watermark when checking compaction success
has been added to the -mm tree. Its filename is
mm-compaction-use-correct-watermark-when-checking-compaction-success.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-use-correct-watermark-when-checking-compaction-success.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-use-correct-watermark-when-checking-compaction-success.patch
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From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm, compaction: use correct watermark when checking compaction success
The __compact_finished() function uses low watermark in a check that has
to pass if the direct compaction is to finish and allocation should
succeed. This is too pessimistic, as the allocation will typically use
min watermark. It may happen that during compaction, we drop below the
low watermark (due to parallel activity), but still form the target
high-order page. By checking against low watermark, we might needlessly
continue compaction.
Similarly, __compaction_suitable() uses low watermark in a check whether
allocation can succeed without compaction. Again, this is unnecessarily
pessimistic.
After this patch, these check will use direct compactor's alloc_flags to
determine the watermark, which is effectively the min watermark.
Link: http://lkml.kernel.org/r/20160810091226.6709-8-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff -puN mm/compaction.c~mm-compaction-use-correct-watermark-when-checking-compaction-success mm/compaction.c
--- a/mm/compaction.c~mm-compaction-use-correct-watermark-when-checking-compaction-success
+++ a/mm/compaction.c
@@ -1316,7 +1316,7 @@ static enum compact_result __compact_fin
return COMPACT_CONTINUE;
/* Compaction run is not finished if the watermark is not met */
- watermark = low_wmark_pages(zone);
+ watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK];
if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
cc->alloc_flags))
@@ -1381,7 +1381,7 @@ static enum compact_result __compaction_
if (is_via_compact_memory(order))
return COMPACT_CONTINUE;
- watermark = low_wmark_pages(zone);
+ watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
/*
* If watermarks for high-order allocation are already met, there
* should be no need for compaction at all.
@@ -1395,7 +1395,7 @@ static enum compact_result __compaction_
* This is because during migration, copies of pages need to be
* allocated and for a short time, the footprint is higher
*/
- watermark += (2UL << order);
+ watermark = low_wmark_pages(zone) + (2UL << order);
if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
alloc_flags, wmark_target))
return COMPACT_SKIPPED;
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-compaction-make-whole_zone-flag-ignore-cached-scanner-positions.patch
mm-compaction-cleanup-unused-functions.patch
mm-compaction-rename-compact_partial-to-compact_success.patch
mm-compaction-dont-recheck-watermarks-after-compact_success.patch
mm-compaction-add-the-ultimate-direct-compaction-priority.patch
mm-compaction-more-reliably-increase-direct-compaction-priority.patch
mm-compaction-use-correct-watermark-when-checking-compaction-success.patch
mm-compaction-create-compact_gap-wrapper.patch
mm-compaction-use-proper-alloc_flags-in-__compaction_suitable.patch
mm-compaction-require-only-min-watermarks-for-non-costly-orders.patch
mm-vmscan-make-compaction_ready-more-accurate-and-readable.patch
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