Compaction returns prematurely with COMPACT_PARTIAL when contended or has fatal
signal pending. This is ok for the callers, but might be misleading in the
traces, as the usual reason to return COMPACT_PARTIAL is that we think the
allocation should succeed. After this patch we distinguish the premature ending
condition in the mm_compaction_finished and mm_compaction_end tracepoints.
The contended status covers the following reasons:
- lock contention or need_resched() detected in async compaction
- fatal signal pending
- too many pages isolated in the zone (only for async compaction)
Further distinguishing the exact reason seems unnecessary for now.
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
---
v2: extend to mm_compaction_end (pointed out by Joonsoo)
include/linux/compaction.h | 1 +
include/trace/events/compaction.h | 3 ++-
mm/compaction.c | 9 ++++++---
3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index f14ba98..4cd4ddf 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -15,6 +15,7 @@
/* For more detailed tracepoint output */
#define COMPACT_NO_SUITABLE_PAGE 5
#define COMPACT_NOT_SUITABLE_ZONE 6
+#define COMPACT_CONTENDED 7
/* When adding new states, please adjust include/trace/events/compaction.h */
/* Used to signal whether compaction detected need_sched() or lock contention */
diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
index 8daa8fa..5604994 100644
--- a/include/trace/events/compaction.h
+++ b/include/trace/events/compaction.h
@@ -16,7 +16,8 @@
EM( COMPACT_PARTIAL, "partial") \
EM( COMPACT_COMPLETE, "complete") \
EM( COMPACT_NO_SUITABLE_PAGE, "no_suitable_page") \
- EMe(COMPACT_NOT_SUITABLE_ZONE, "not_suitable_zone")
+ EM( COMPACT_NOT_SUITABLE_ZONE, "not_suitable_zone") \
+ EMe(COMPACT_CONTENDED, "contended")
#ifdef CONFIG_ZONE_DMA
#define IFDEF_ZONE_DMA(X) X
diff --git a/mm/compaction.c b/mm/compaction.c
index a5849c4..de3e1e7 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1202,7 +1202,7 @@ static int __compact_finished(struct zone *zone, struct compact_control *cc,
unsigned long watermark;
if (cc->contended || fatal_signal_pending(current))
- return COMPACT_PARTIAL;
+ return COMPACT_CONTENDED;
/* Compaction run completes if the migrate and free scanner meet */
if (compact_scanners_met(cc)) {
@@ -1393,7 +1393,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
switch (isolate_migratepages(zone, cc)) {
case ISOLATE_ABORT:
- ret = COMPACT_PARTIAL;
+ ret = COMPACT_CONTENDED;
putback_movable_pages(&cc->migratepages);
cc->nr_migratepages = 0;
goto out;
@@ -1424,7 +1424,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
* and we want compact_finished() to detect it
*/
if (err == -ENOMEM && !compact_scanners_met(cc)) {
- ret = COMPACT_PARTIAL;
+ ret = COMPACT_CONTENDED;
goto out;
}
}
@@ -1477,6 +1477,9 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
cc->free_pfn, end_pfn, sync, ret);
+ if (ret == COMPACT_CONTENDED)
+ ret = COMPACT_PARTIAL;
+
return ret;
}
--
2.5.1
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