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| author | Vlastimil Babka <vbabka@suse.cz> | 2016-10-07 16:57:53 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-07 18:46:27 -0700 |
| commit | 9861a62c335cd34a2b6b25aaaf5898e8370299ec (patch) | |
| tree | 4eb21fe16acfb2e229422de1927bfcb152781829 /mm/compaction.c | |
| parent | f2b8228c5f99a92bc07efd36f8dc840e0705a266 (diff) | |
| download | linux-9861a62c335cd34a2b6b25aaaf5898e8370299ec.tar.bz2 | |
mm, compaction: create compact_gap wrapper
Compaction uses a watermark gap of (2UL << order) pages at various
places and it's not immediately obvious why. Abstract it through a
compact_gap() wrapper to create a single place with a thorough
explanation.
[vbabka@suse.cz: clarify the comment of compact_gap()]
Link: http://lkml.kernel.org/r/7b6aed1f-fdf8-2063-9ff4-bbe4de712d37@suse.cz
Link: http://lkml.kernel.org/r/20160810091226.6709-9-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
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 | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index e2618ac062a6..bbf41ee99142 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1391,11 +1391,10 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order, return COMPACT_SUCCESS; /* - * Watermarks for order-0 must be met for compaction. Note the 2UL. - * This is because during migration, copies of pages need to be - * allocated and for a short time, the footprint is higher + * Watermarks for order-0 must be met for compaction to be able to + * isolate free pages for migration targets. */ - watermark = low_wmark_pages(zone) + (2UL << order); + watermark = low_wmark_pages(zone) + compact_gap(order); if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx, alloc_flags, wmark_target)) return COMPACT_SKIPPED; |