[Xenial PATCH 03/11] mm, compaction: distinguish COMPACT_DEFERRED from COMPACT_SKIPPED
Thadeu Lima de Souza Cascardo
cascardo at canonical.com
Tue Jan 24 16:28:31 UTC 2017
From: Michal Hocko <mhocko at suse.com>
BugLink: https://bugs.launchpad.net/bugs/1655842
try_to_compact_pages() can currently return COMPACT_SKIPPED even when
the compaction is defered for some zone just because zone DMA is skipped
in 99% of cases due to watermark checks. This makes COMPACT_DEFERRED
basically unusable for the page allocator as a feedback mechanism.
Make sure we distinguish those two states properly and switch their
ordering in the enum. This would mean that the COMPACT_SKIPPED will be
returned only when all eligible zones are skipped.
As a result COMPACT_DEFERRED handling for THP in __alloc_pages_slowpath
will be more precise and we would bail out rather than reclaim.
Signed-off-by: Michal Hocko <mhocko at suse.com>
Acked-by: Vlastimil Babka <vbabka at suse.cz>
Acked-by: Hillf Danton <hillf.zj at alibaba-inc.com>
Cc: David Rientjes <rientjes at google.com>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: Joonsoo Kim <js1304 at gmail.com>
Cc: Mel Gorman <mgorman at techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov at virtuozzo.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry picked from commit 1d4746d395975e0ff5103e20ab169d1a95b4ef9e)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
---
include/linux/compaction.h | 7 +++++--
include/trace/events/compaction.h | 2 +-
mm/compaction.c | 8 +++++---
3 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 9c7d7a2..78eeaf6 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -4,13 +4,16 @@
/* Return values for compact_zone() and try_to_compact_pages() */
/* When adding new states, please adjust include/trace/events/compaction.h */
enum compact_result {
- /* compaction didn't start as it was deferred due to past failures */
- COMPACT_DEFERRED,
/*
* compaction didn't start as it was not possible or direct reclaim
* was more suitable
*/
COMPACT_SKIPPED,
+ /* compaction didn't start as it was deferred due to past failures */
+ COMPACT_DEFERRED,
+ /* compaction not active last round */
+ COMPACT_INACTIVE = COMPACT_DEFERRED,
+
/* compaction should continue to another pageblock */
COMPACT_CONTINUE,
/*
diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
index c92d1e1..ace0a02 100644
--- a/include/trace/events/compaction.h
+++ b/include/trace/events/compaction.h
@@ -10,8 +10,8 @@
#include <trace/events/gfpflags.h>
#define COMPACTION_STATUS \
- EM( COMPACT_DEFERRED, "deferred") \
EM( COMPACT_SKIPPED, "skipped") \
+ EM( COMPACT_DEFERRED, "deferred") \
EM( COMPACT_CONTINUE, "continue") \
EM( COMPACT_PARTIAL, "partial") \
EM( COMPACT_COMPLETE, "complete") \
diff --git a/mm/compaction.c b/mm/compaction.c
index c74dd55..2ee037d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1522,7 +1522,7 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
int may_perform_io = gfp_mask & __GFP_IO;
struct zoneref *z;
struct zone *zone;
- enum compact_result rc = COMPACT_DEFERRED;
+ enum compact_result rc = COMPACT_SKIPPED;
int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */
*contended = COMPACT_CONTENDED_NONE;
@@ -1539,8 +1539,10 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
enum compact_result status;
int zone_contended;
- if (compaction_deferred(zone, order))
+ if (compaction_deferred(zone, order)) {
+ rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
continue;
+ }
status = compact_zone_order(zone, order, gfp_mask, mode,
&zone_contended, alloc_flags,
@@ -1611,7 +1613,7 @@ break_loop:
* If at least one zone wasn't deferred or skipped, we report if all
* zones that were tried were lock contended.
*/
- if (rc > COMPACT_SKIPPED && all_zones_contended)
+ if (rc > COMPACT_INACTIVE && all_zones_contended)
*contended = COMPACT_CONTENDED_LOCK;
return rc;
--
2.9.3
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