Messages in this thread | | | Subject | Re: [PATCH v3 13/17] mm, compaction: use correct watermark when checking allocation success | From | Vlastimil Babka <> | Date | Mon, 18 Jul 2016 11:23:38 +0200 |
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On 07/06/2016 07:47 AM, Joonsoo Kim wrote: > On Fri, Jun 24, 2016 at 11:54:33AM +0200, Vlastimil Babka wrote: >> The __compact_finished() function uses low watermark in a check that has to >> pass if the direct compaction is to finish and allocation should succeed. This >> is too pessimistic, as the allocation will typically use min watermark. It may >> happen that during compaction, we drop below the low watermark (due to parallel >> activity), but still form the target high-order page. By checking against low >> watermark, we might needlessly continue compaction. >> >> Similarly, __compaction_suitable() uses low watermark in a check whether >> allocation can succeed without compaction. Again, this is unnecessarily >> pessimistic. >> >> After this patch, these check will use direct compactor's alloc_flags to >> determine the watermark, which is effectively the min watermark. >> >> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> >> Acked-by: Michal Hocko <mhocko@suse.com> >> --- >> mm/compaction.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index 76897850c3c2..371760a85085 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -1320,7 +1320,7 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_ >> return COMPACT_CONTINUE; >> >> /* Compaction run is not finished if the watermark is not met */ >> - watermark = low_wmark_pages(zone); >> + watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK]; > > finish condition is changed. We have two more watermark checks in > try_to_compact_pages() and kcompactd_do_work() and they should be > changed too.
Ugh, I've completely missed them. Thanks for catching this, hopefully fixing that will improve the results.
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