mm, compaction: distinguish COMPACT_DEFERRED from COMPACT_SKIPPED
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@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 706cbf0..11f2287 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,
/*