The patch titled
Subject: mm, compaction: check early for huge pages encountered by the migration scanner
has been added to the -mm tree. Its filename is
mm-compaction-check-early-for-huge-pages-encountered-by-the-migration-scanner.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-check-early-for-huge-pages-encountered-by-the-migration-scanner.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-check-early-for-huge-pages-encountered-by-the-migration-scanner.patch
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm, compaction: check early for huge pages encountered by the migration scanner
When scanning for sources or targets, PageCompound is checked for huge
pages as they can be skipped quickly but it happens relatively late after
a lot of setup and checking. This patch short-cuts the check to make it
earlier. It might still change when the lock is acquired but this has
less overhead overall. The free scanner advances but the migration
scanner does not. Typically the free scanner encounters more movable
blocks that change state over the lifetime of the system and also tends to
scan more aggressively as it's actively filling its portion of the
physical address space with data. This could change in the future but for
the moment, this worked better in practice and incurred fewer scan
restarts.
The impact on latency and allocation success rates is marginal but the
free scan rates are reduced by 15% and system CPU usage is reduced by
3.3%. The 2-socket results are not materially different.
Link: http://lkml.kernel.org/r/20190118175136.31341-15-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: YueHaibing <yuehaibing@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
--- a/mm/compaction.c~mm-compaction-check-early-for-huge-pages-encountered-by-the-migration-scanner
+++ a/mm/compaction.c
@@ -1061,6 +1061,9 @@ static bool suitable_migration_source(st
{
int block_mt;
+ if (pageblock_skip_persistent(page))
+ return false;
+
if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
return true;
@@ -1695,12 +1698,17 @@ static isolate_migrate_t isolate_migrate
continue;
/*
- * For async compaction, also only scan in MOVABLE blocks.
- * Async compaction is optimistic to see if the minimum amount
- * of work satisfies the allocation.
+ * For async compaction, also only scan in MOVABLE blocks
+ * without huge pages. Async compaction is optimistic to see
+ * if the minimum amount of work satisfies the allocation.
+ * The cached PFN is updated as it's possible that all
+ * remaining blocks between source and target are unsuitable
+ * and the compaction scanners fail to meet.
*/
- if (!suitable_migration_source(cc, page))
+ if (!suitable_migration_source(cc, page)) {
+ update_cached_migrate(cc, block_end_pfn);
continue;
+ }
/* Perform the isolation */
low_pfn = isolate_migratepages_block(cc, low_pfn,
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-compaction-shrink-compact_control.patch
mm-compaction-rearrange-compact_control.patch
mm-compaction-remove-last_migrated_pfn-from-compact_control.patch
mm-compaction-remove-unnecessary-zone-parameter-in-some-instances.patch
mm-compaction-rename-map_pages-to-split_map_pages.patch
mm-migrate-immediately-fail-migration-of-a-page-with-no-migration-handler.patch
mm-compaction-always-finish-scanning-of-a-full-pageblock.patch
mm-compaction-ignore-the-fragmentation-avoidance-boost-for-isolation-and-compaction.patch
mm-compaction-use-free-lists-to-quickly-locate-a-migration-source.patch
mm-compaction-keep-migration-source-private-to-a-single-compaction-instance.patch
mm-compaction-use-free-lists-to-quickly-locate-a-migration-target.patch
mm-compaction-avoid-rescanning-the-same-pageblock-multiple-times.patch
mm-compaction-finish-pageblock-scanning-on-contention.patch
mm-compaction-check-early-for-huge-pages-encountered-by-the-migration-scanner.patch
mm-compaction-keep-cached-migration-pfns-synced-for-unusable-pageblocks.patch
mm-compaction-rework-compact_should_abort-as-compact_check_resched.patch
mm-compaction-do-not-consider-a-need-to-reschedule-as-contention.patch
mm-compaction-reduce-premature-advancement-of-the-migration-target-scanner.patch
mm-compaction-round-robin-the-order-while-searching-the-free-lists-for-a-target.patch
mm-compaction-sample-pageblocks-for-free-pages.patch
mm-compaction-be-selective-about-what-pageblocks-to-clear-skip-hints.patch
mm-compaction-capture-a-page-under-direct-compaction.patch
