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Groups > linux.kernel > #1459885
| From | Vlastimil Babka <vbabka@suse.cz> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v6 09/11] mm, compaction: use proper alloc_flags in __compaction_suitable() |
| Date | 2016-08-10 22:50 +0200 |
| Message-ID | <s4IBQ-1DK-13@gated-at.bofh.it> (permalink) |
| References | <s4GgI-79-119@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
The __compaction_suitable() function checks the low watermark plus a
compact_gap() gap to decide if there's enough free memory to perform
compaction. This check uses direct compactor's alloc_flags, but that's wrong,
since these flags are not applicable for freepage isolation.
For example, alloc_flags may indicate access to memory reserves, making
compaction proceed, and then fail watermark check during the isolation.
A similar problem exists for ALLOC_CMA, which may be part of alloc_flags, but
not during freepage isolation. In this case however it makes sense to use
ALLOC_CMA both in __compaction_suitable() and __isolate_free_page(), since
there's actually nothing preventing the freepage scanner to isolate from CMA
pageblocks, with the assumption that a page that could be migrated once by
compaction can be migrated also later by CMA allocation. Thus we should count
pages in CMA pageblocks when considering compaction suitability and when
isolating freepages.
To sum up, this patch should remove some false positives from
__compaction_suitable(), and allow compaction to proceed when free pages
required for compaction reside in the CMA pageblocks.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/compaction.c | 12 ++++++++++--
mm/page_alloc.c | 2 +-
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index ae6ecf8f8e70..80eaf9fff114 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1392,11 +1392,19 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
/*
* Watermarks for order-0 must be met for compaction to be able to
- * isolate free pages for migration targets.
+ * isolate free pages for migration targets. This means that the
+ * watermark and alloc_flags have to match, or be more pessimistic than
+ * the check in __isolate_free_page(). We don't use the direct
+ * compactor's alloc_flags, as they are not relevant for freepage
+ * isolation. We however do use the direct compactor's classzone_idx to
+ * skip over zones where lowmem reserves would prevent allocation even
+ * if compaction succeeds.
+ * ALLOC_CMA is used, as pages in CMA pageblocks are considered
+ * suitable migration targets
*/
watermark = low_wmark_pages(zone) + compact_gap(order);
if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
- alloc_flags, wmark_target))
+ ALLOC_CMA, wmark_target))
return COMPACT_SKIPPED;
/*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b28517b918b0..621e4211ce16 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2493,7 +2493,7 @@ int __isolate_free_page(struct page *page, unsigned int order)
if (!is_migrate_isolate(mt)) {
/* Obey watermarks as if the page was being allocated */
watermark = low_wmark_pages(zone) + (1 << order);
- if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+ if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
return 0;
__mod_zone_freepage_state(zone, -(1UL << order), mt);
--
2.9.2
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[PATCH v6 00/11] make direct compaction more deterministic Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 20:20 +0200
[PATCH v6 06/11] mm, compaction: more reliably increase direct compaction priority Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 22:50 +0200
Re: [PATCH v6 06/11] mm, compaction: more reliably increase direct compaction priority Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-08-16 08:10 +0200
Re: [PATCH v6 06/11] mm, compaction: more reliably increase direct compaction priority Vlastimil Babka <vbabka@suse.cz> - 2016-08-16 08:40 +0200
Re: [PATCH v6 06/11] mm, compaction: more reliably increase direct compaction priority Michal Hocko <mhocko@kernel.org> - 2016-08-18 11:20 +0200
Re: [PATCH v6 06/11] mm, compaction: more reliably increase direct compaction priority Vlastimil Babka <vbabka@suse.cz> - 2016-08-18 11:50 +0200
Re: [PATCH v6 06/11] mm, compaction: more reliably increase direct compaction priority Michal Hocko <mhocko@kernel.org> - 2016-08-18 12:00 +0200
[PATCH v6 09/11] mm, compaction: use proper alloc_flags in __compaction_suitable() Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 22:50 +0200
[PATCH v6 01/11] mm, compaction: make whole_zone flag ignore cached scanner positions Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 22:50 +0200
[PATCH v6 07/11] mm, compaction: use correct watermark when checking compaction success Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 22:50 +0200
[PATCH v6 08/11] mm, compaction: create compact_gap wrapper Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 22:50 +0200
Re: [PATCH v6 08/11] mm, compaction: create compact_gap wrapper Vlastimil Babka <vbabka@suse.cz> - 2016-08-16 08:20 +0200
Re: [PATCH v6 08/11] mm, compaction: create compact_gap wrapper Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-08-16 08:40 +0200
Re: [PATCH v6 08/11] mm, compaction: create compact_gap wrapper Vlastimil Babka <vbabka@suse.cz> - 2016-08-18 14:20 +0200
Re: [PATCH v6 08/11] mm, compaction: create compact_gap wrapper Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-08-16 08:20 +0200
[PATCH v6 03/11] mm, compaction: rename COMPACT_PARTIAL to COMPACT_SUCCESS Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 22:50 +0200
Re: [PATCH v6 03/11] mm, compaction: rename COMPACT_PARTIAL to COMPACT_SUCCESS Michal Hocko <mhocko@kernel.org> - 2016-08-18 13:10 +0200
[PATCH v6 02/11] mm, compaction: cleanup unused functions Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 23:30 +0200
[PATCH v6 10/11] mm, compaction: require only min watermarks for non-costly orders Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 23:30 +0200
Re: [PATCH v6 10/11] mm, compaction: require only min watermarks for non-costly orders Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-08-16 08:20 +0200
Re: [PATCH v6 10/11] mm, compaction: require only min watermarks for non-costly orders Vlastimil Babka <vbabka@suse.cz> - 2016-08-16 08:40 +0200
Re: [PATCH v6 10/11] mm, compaction: require only min watermarks for non-costly orders Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-08-16 08:50 +0200
Re: [PATCH v6 10/11] mm, compaction: require only min watermarks for non-costly orders Vlastimil Babka <vbabka@suse.cz> - 2016-08-18 14:30 +0200
[PATCH v6 05/11] mm, compaction: add the ultimate direct compaction priority Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 23:30 +0200
Re: [PATCH v6 05/11] mm, compaction: add the ultimate direct compaction priority Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-08-16 08:00 +0200
Re: [PATCH v6 05/11] mm, compaction: add the ultimate direct compaction priority Vlastimil Babka <vbabka@suse.cz> - 2016-08-18 14:30 +0200
[PATCH v6 11/11] mm, vmscan: make compaction_ready() more accurate and readable Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 23:30 +0200
[PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS Vlastimil Babka <vbabka@suse.cz> - 2016-08-10 23:30 +0200
Re: [PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-08-16 08:10 +0200
Re: [PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS Vlastimil Babka <vbabka@suse.cz> - 2016-08-16 08:20 +0200
Re: [PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS Vlastimil Babka <vbabka@suse.cz> - 2016-08-18 14:00 +0200
Re: [PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS Michal Hocko <mhocko@kernel.org> - 2016-08-18 11:10 +0200
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