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| author | Vlastimil Babka <vbabka@suse.cz> | 2017-05-08 15:54:49 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-05-08 17:15:10 -0700 |
| commit | 282722b0d258ec23fc79d80165418fee83f01736 (patch) | |
| tree | 01b33534bae259a2ad1ce7acf98e5b5632bb467b /mm/compaction.c | |
| parent | d39773a0622c267fef3f79e3b1f0e7bdbad8a1a8 (diff) | |
| download | linux-282722b0d258ec23fc79d80165418fee83f01736.tar.gz linux-282722b0d258ec23fc79d80165418fee83f01736.tar.bz2 linux-282722b0d258ec23fc79d80165418fee83f01736.zip | |
mm, compaction: restrict async compaction to pageblocks of same migratetype
The migrate scanner in async compaction is currently limited to
MIGRATE_MOVABLE pageblocks. This is a heuristic intended to reduce
latency, based on the assumption that non-MOVABLE pageblocks are
unlikely to contain movable pages.
However, with the exception of THP's, most high-order allocations are
not movable. Should the async compaction succeed, this increases the
chance that the non-MOVABLE allocations will fallback to a MOVABLE
pageblock, making the long-term fragmentation worse.
This patch attempts to help the situation by changing async direct
compaction so that the migrate scanner only scans the pageblocks of the
requested migratetype. If it's a non-MOVABLE type and there are such
pageblocks that do contain movable pages, chances are that the
allocation can succeed within one of such pageblocks, removing the need
for a fallback. If that fails, the subsequent sync attempt will ignore
this restriction.
In testing based on 4.9 kernel with stress-highalloc from mmtests
configured for order-4 GFP_KERNEL allocations, this patch has reduced
the number of unmovable allocations falling back to movable pageblocks
by 30%. The number of movable allocations falling back is reduced by
12%.
Link: http://lkml.kernel.org/r/20170307131545.28577-8-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/compaction.c')
| -rw-r--r-- | mm/compaction.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 365b3c8ae943..206847d35978 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -986,10 +986,17 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, static bool suitable_migration_source(struct compact_control *cc, struct page *page) { - if (cc->mode != MIGRATE_ASYNC) + int block_mt; + + if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction) return true; - return is_migrate_movable(get_pageblock_migratetype(page)); + block_mt = get_pageblock_migratetype(page); + + if (cc->migratetype == MIGRATE_MOVABLE) + return is_migrate_movable(block_mt); + else + return block_mt == cc->migratetype; } /* Returns true if the page is within a block suitable for migration to */ |