The patch titled
Subject: mm/compaction: count pages and stop correctly during page isolation
has been added to the -mm tree. Its filename is
mm-compaction-count-pages-and-stop-correctly-during-page-isolation.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-count-pages-and-stop-correctly-during-page-isolation.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-count-pages-and-stop-correctly-during-page-isolation.patch
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------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm/compaction: count pages and stop correctly during page isolation
In isolate_migratepages_block, when cc->alloc_contig is true, we are able
to isolate compound pages, nr_migratepages and nr_isolated did not count
compound pages correctly, causing us to isolate more pages than we
thought. Use thp_nr_pages to count pages. Otherwise, we might be trapped
in too_many_isolated while loop, since the actual isolated pages can go up
to COMPACT_CLUSTER_MAX*512=3D16384, where COMPACT_CLUSTER_MAX is 32, since
we stop isolation after cc->nr_migratepages reaches to
COMPACT_CLUSTER_MAX.
In addition, after we fix the issue above, cc->nr_migratepages could never
be equal to COMPACT_CLUSTER_MAX if compound pages are isolated, thus page
isolation could not stop as we intended. Change the isolation stop
condition to >=3D.
Link: https://lkml.kernel.org/r/20201029200435.3386066-1-zi.yan@xxxxxxxx
Fixes: 1da2f328fa64 ("cmm,thp,compaction,cma: allow THP migration for CMA allocations")
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/mm/compaction.c~mm-compaction-count-pages-and-stop-correctly-during-page-isolation
+++ a/mm/compaction.c
@@ -1012,8 +1012,8 @@ isolate_migratepages_block(struct compac
isolate_success:
list_add(&page->lru, &cc->migratepages);
- cc->nr_migratepages++;
- nr_isolated++;
+ cc->nr_migratepages += thp_nr_pages(page);
+ nr_isolated += thp_nr_pages(page);
/*
* Avoid isolating too much unless this block is being
@@ -1021,7 +1021,7 @@ isolate_success:
* or a lock is contended. For contention, isolate quickly to
* potentially remove one source of contention.
*/
- if (cc->nr_migratepages == COMPACT_CLUSTER_MAX &&
+ if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX &&
!cc->rescan && !cc->contended) {
++low_pfn;
break;
@@ -1132,7 +1132,7 @@ isolate_migratepages_range(struct compac
if (!pfn)
break;
- if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
+ if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX)
break;
}
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-compaction-count-pages-and-stop-correctly-during-page-isolation.patch
