Messages in this thread Patch in this message | | | From | Vlastimil Babka <> | Subject | [PATCH v2 02/10] mm, compaction: remove redundant watermark check in compact_finished() | Date | Fri, 10 Feb 2017 18:23:35 +0100 |
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When detecting whether compaction has succeeded in forming a high-order page, __compact_finished() employs a watermark check, followed by an own search for a suitable page in the freelists. This is not ideal for two reasons:
- The watermark check also searches high-order freelists, but has a less strict criteria wrt fallback. It's therefore redundant and waste of cycles. This was different in the past when high-order watermark check attempted to apply reserves to high-order pages.
- The watermark check might actually fail due to lack of order-0 pages. Compaction can't help with that, so there's no point in continuing because of that. It's possible that high-order page still exists and it terminates.
This patch therefore removes the watermark check. This should save some cycles and terminate compaction sooner in some cases.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz> --- mm/compaction.c | 8 -------- 1 file changed, 8 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c index 0409a4ad6ea1..fc88e7b6fe37 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1291,7 +1291,6 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_ const int migratetype) { unsigned int order; - unsigned long watermark; if (cc->contended || fatal_signal_pending(current)) return COMPACT_CONTENDED; @@ -1319,13 +1318,6 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_ if (is_via_compact_memory(cc->order)) return COMPACT_CONTINUE; - /* Compaction run is not finished if the watermark is not met */ - watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK]; - - if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx, - cc->alloc_flags)) - return COMPACT_CONTINUE; - /* Direct compactor: Is a suitable page free? */ for (order = cc->order; order < MAX_ORDER; order++) { struct free_area *area = &zone->free_area[order]; -- 2.11.0
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