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authorVlastimil Babka <vbabka@suse.cz>2019-09-23 15:37:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-24 15:54:10 -0700
commit494330855641269c8a49f1580f0d4e2ead693245 (patch)
tree4f168ac383f3764c83881643037ee70256bff225 /mm/page_alloc.c
parent5ee04716c46ce58989b1256a98af1af89f385db8 (diff)
mm, compaction: raise compaction priority after it withdrawns
Mike Kravetz reports that "hugetlb allocations could stall for minutes or hours when should_compact_retry() would return true more often then it should. Specifically, this was in the case where compact_result was COMPACT_DEFERRED and COMPACT_PARTIAL_SKIPPED and no progress was being made." The problem is that the compaction_withdrawn() test in should_compact_retry() includes compaction outcomes that are only possible on low compaction priority, and results in a retry without increasing the priority. This may result in furter reclaim, and more incomplete compaction attempts. With this patch, compaction priority is raised when possible, or should_compact_retry() returns false. The COMPACT_SKIPPED result doesn't really fit together with the other outcomes in compaction_withdrawn(), as that's a result caused by insufficient order-0 pages, not due to low compaction priority. With this patch, it is moved to a new compaction_needs_reclaim() function, and for that outcome we keep the current logic of retrying if it looks like reclaim will be able to help. Link: http://lkml.kernel.org/r/20190806014744.15446-4-mike.kravetz@oracle.com Reported-by: Mike Kravetz <mike.kravetz@oracle.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Tested-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Hillf Danton <hdanton@sina.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c16
1 files changed, 12 insertions, 4 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index df566c0f6729..591e026534c2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3955,14 +3955,22 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
goto check_priority;
/*
+ * compaction was skipped because there are not enough order-0 pages
+ * to work with, so we retry only if it looks like reclaim can help.
+ */
+ if (compaction_needs_reclaim(compact_result)) {
+ ret = compaction_zonelist_suitable(ac, order, alloc_flags);
+ goto out;
+ }
+
+ /*
* make sure the compaction wasn't deferred or didn't bail out early
* due to locks contention before we declare that we should give up.
- * But do not retry if the given zonelist is not suitable for
- * compaction.
+ * But the next retry should use a higher priority if allowed, so
+ * we don't just keep bailing out endlessly.
*/
if (compaction_withdrawn(compact_result)) {
- ret = compaction_zonelist_suitable(ac, order, alloc_flags);
- goto out;
+ goto check_priority;
}
/*