| Message ID | 20230515113344.6869-3-mgorman@techsingularity.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Follow-up "Fix excessive CPU usage during compaction" | expand |
On 5/15/23 13:33, Mel Gorman wrote: > fast_find_migrateblock relies on skip hints to avoid rescanning a recently > selected pageblock but compact_zone() only forces the pageblock scan > completion to set the skip hint if in direct compaction. While this > prevents direct compaction repeatedly scanning a subset of blocks due > to fast_find_migrateblock(), it does not prevent proactive compaction, > node compaction and kcompactd encountering the same problem described > in commit cfccd2e63e7e ("mm, compaction: finish pageblocks on complete > migration failure"). > > Force the scan completion of a pageblock to set the skip hint if skip > hints are obeyed to prevent fast_find_migrateblock() repeatedly selecting > a subset of pageblocks. > > Suggested-by: Vlastimil Babka <vbabka@suse.cz> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/compaction.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 81791c124bb8..accc6568091a 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -2456,7 +2456,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > } > /* > * If an ASYNC or SYNC_LIGHT fails to migrate a page > - * within the current order-aligned block, scan the > + * within the current order-aligned block and > + * fast_find_migrateblock may be used then scan the > * remainder of the pageblock. This will mark the > * pageblock "skip" to avoid rescanning in the near > * future. This will isolate more pages than necessary > @@ -2465,7 +2466,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > * recently partially scanned. > */ > if (!pageblock_aligned(cc->migrate_pfn) && > - cc->direct_compaction && !cc->finish_pageblock && > + !cc->ignore_skip_hint && !cc->finish_pageblock && > (cc->mode < MIGRATE_SYNC)) { > cc->finish_pageblock = true; >
diff --git a/mm/compaction.c b/mm/compaction.c index 81791c124bb8..accc6568091a 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -2456,7 +2456,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) } /* * If an ASYNC or SYNC_LIGHT fails to migrate a page - * within the current order-aligned block, scan the + * within the current order-aligned block and + * fast_find_migrateblock may be used then scan the * remainder of the pageblock. This will mark the * pageblock "skip" to avoid rescanning in the near * future. This will isolate more pages than necessary @@ -2465,7 +2466,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) * recently partially scanned. */ if (!pageblock_aligned(cc->migrate_pfn) && - cc->direct_compaction && !cc->finish_pageblock && + !cc->ignore_skip_hint && !cc->finish_pageblock && (cc->mode < MIGRATE_SYNC)) { cc->finish_pageblock = true;
fast_find_migrateblock relies on skip hints to avoid rescanning a recently selected pageblock but compact_zone() only forces the pageblock scan completion to set the skip hint if in direct compaction. While this prevents direct compaction repeatedly scanning a subset of blocks due to fast_find_migrateblock(), it does not prevent proactive compaction, node compaction and kcompactd encountering the same problem described in commit cfccd2e63e7e ("mm, compaction: finish pageblocks on complete migration failure"). Force the scan completion of a pageblock to set the skip hint if skip hints are obeyed to prevent fast_find_migrateblock() repeatedly selecting a subset of pageblocks. Suggested-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Mel Gorman <mgorman@techsingularity.net> --- mm/compaction.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)