mm, compaction: distinguish contended status in tracepoints

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 <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Vlastimil Babka 2015-11-05 18:48:02 -08:00 • committed by Linus Torvalds
commit 2d1e10412c
3 changed files with 9 additions and 4 deletions

View file

@ -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 @@ out:
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;
}