diff options
| author | Vlastimil Babka <vbabka@suse.cz> | 2019-09-23 15:37:32 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-24 15:54:10 -0700 |
| commit | 494330855641269c8a49f1580f0d4e2ead693245 (patch) | |
| tree | 4f168ac383f3764c83881643037ee70256bff225 /mm | |
| parent | 5ee04716c46ce58989b1256a98af1af89f385db8 (diff) | |
| download | lwn-494330855641269c8a49f1580f0d4e2ead693245.tar.gz lwn-494330855641269c8a49f1580f0d4e2ead693245.zip | |
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')
| -rw-r--r-- | mm/page_alloc.c | 16 |
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; } /* |