Re: [patch] mm, thp: abort compaction if migration page cannot be charged to memcg
From: Minchan Kim <minchan@kernel.org>
Date: 2012-06-21 08:11:35
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On 06/21/2012 03:52 PM, David Rientjes wrote:
If page migration cannot charge the new page to the memcg, migrate_pages() will return -ENOMEM. This isn't considered in memory compaction however, and the loop continues to iterate over all pageblocks trying in a futile attempt to continue migrations which are only bound to fail.
Hmm, it might be dumb question. I imagine that pages in next pageblock could be in another memcg so it could be successful. Why should we stop compaction once it fails to migrate pages in current pageblock/memcg?
quoted hunk ↗ jump to hunk
This will short circuit and fail memory compaction if migrate_pages() returns -ENOMEM. COMPACT_PARTIAL is returned in case some migrations were successful so that the page allocator will retry. Signed-off-by: David Rientjes <rientjes@google.com> --- mm/compaction.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)diff --git a/mm/compaction.c b/mm/compaction.c --- a/mm/compaction.c +++ b/mm/compaction.c@@ -701,8 +701,11 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) if (err) { putback_lru_pages(&cc->migratepages); cc->nr_migratepages = 0; + if (err == -ENOMEM) { + ret = COMPACT_PARTIAL; + goto out; + } } - } out:
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