From: Hugh Dickins <[email protected]>
commit ff59909a077b3c51c168cb658601c6b63136a347 upstream.
The vmstat interfaces are good at hiding negative counts (at least when
CONFIG_SMP); but if you peer behind the curtain, you find that
nr_isolated_anon and nr_isolated_file soon go negative, and grow ever
more negative: so they can absorb larger and larger numbers of isolated
pages, yet still appear to be zero.
I'm happy to avoid a congestion_wait() when too_many_isolated() myself;
but I guess it's there for a good reason, in which case we ought to get
too_many_isolated() working again.
The imbalance comes from isolate_migratepages()'s ISOLATE_ABORT case:
putback_movable_pages() decrements the NR_ISOLATED counts, but we forgot
to call acct_isolated() to increment them.
It is possible that the bug whcih this patch fixes could cause OOM kills
when the system still has a lot of reclaimable page cache.
Fixes: edc2ca612496 ("mm, compaction: move pageblock checks up from
isolate_migratepages_range()")
Signed-off-by: Hugh Dickins <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Acked-by: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
mm/compaction.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 71e613e..b47f08e 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1027,8 +1027,10 @@ static isolate_migrate_t isolate_migratepages(struct
zone *zone,
low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn,
isolate_mode);
- if (!low_pfn || cc->contended)
+ if (!low_pfn || cc->contended) {
+ acct_isolated(zone, cc);
return ISOLATE_ABORT;
+ }
/*
* Either we isolated something and proceed with migration. Or
--
2.1.0
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