diff mbox

[Xenial,03/11] mm, compaction: distinguish COMPACT_DEFERRED from COMPACT_SKIPPED

Message ID 20170124162839.6355-4-cascardo@canonical.com
State New
Headers show

Commit Message

Thadeu Lima de Souza Cascardo Jan. 24, 2017, 4:28 p.m. UTC 
From: Michal Hocko <mhocko@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@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>
(cherry picked from commit 1d4746d395975e0ff5103e20ab169d1a95b4ef9e)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@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 mbox

Patch

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;