From 8854c55f54bcc104e3adae42abe16948286ec75c Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 5 Mar 2019 15:45:18 -0800 Subject: mm, compaction: keep cached migration PFNs synced for unusable pageblocks Migrate has separate cached PFNs for ASYNC and SYNC* migration on the basis that some migrations will fail in ASYNC mode. However, if the cached PFNs match at the start of scanning and pageblocks are skipped due to having no isolation candidates, then the sync state does not matter. This patch keeps matching cached PFNs in sync until a pageblock with isolation candidates is found. The actual benefit is marginal given that the sync scanner following the async scanner will often skip a number of pageblocks but it's useless work. Any benefit depends heavily on whether the scanners restarted recently. Link: http://lkml.kernel.org/r/20190118175136.31341-16-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Cc: Andrea Arcangeli Cc: Dan Carpenter Cc: David Rientjes Cc: YueHaibing Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'mm/compaction.c') diff --git a/mm/compaction.c b/mm/compaction.c index e609415059e8..78ae182aaf34 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1971,6 +1971,7 @@ static enum compact_result compact_zone(struct compact_control *cc) unsigned long end_pfn = zone_end_pfn(cc->zone); unsigned long last_migrated_pfn; const bool sync = cc->mode != MIGRATE_ASYNC; + bool update_cached; cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask); ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags, @@ -2018,6 +2019,17 @@ static enum compact_result compact_zone(struct compact_control *cc) last_migrated_pfn = 0; + /* + * Migrate has separate cached PFNs for ASYNC and SYNC* migration on + * the basis that some migrations will fail in ASYNC mode. However, + * if the cached PFNs match and pageblocks are skipped due to having + * no isolation candidates, then the sync state does not matter. + * Until a pageblock with isolation candidates is found, keep the + * cached PFNs in sync to avoid revisiting the same blocks. + */ + update_cached = !sync && + cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1]; + trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, cc->free_pfn, end_pfn, sync); @@ -2049,6 +2061,11 @@ static enum compact_result compact_zone(struct compact_control *cc) last_migrated_pfn = 0; goto out; case ISOLATE_NONE: + if (update_cached) { + cc->zone->compact_cached_migrate_pfn[1] = + cc->zone->compact_cached_migrate_pfn[0]; + } + /* * We haven't isolated and migrated anything, but * there might still be unflushed migrations from @@ -2056,6 +2073,7 @@ static enum compact_result compact_zone(struct compact_control *cc) */ goto check_drain; case ISOLATE_SUCCESS: + update_cached = false; last_migrated_pfn = start_pfn; ; } -- cgit v1.2.3