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>alistair/sunxi64-5.4-dsi
parent
5ee04716c4
commit
4943308556
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@ -129,11 +129,8 @@ static inline bool compaction_failed(enum compact_result result)
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return false;
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return false;
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}
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}
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/*
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/* Compaction needs reclaim to be performed first, so it can continue. */
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* Compaction has backed off for some reason. It might be throttling or
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static inline bool compaction_needs_reclaim(enum compact_result result)
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* lock contention. Retrying is still worthwhile.
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*/
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static inline bool compaction_withdrawn(enum compact_result result)
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{
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{
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/*
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/*
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* Compaction backed off due to watermark checks for order-0
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* Compaction backed off due to watermark checks for order-0
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@ -142,6 +139,16 @@ static inline bool compaction_withdrawn(enum compact_result result)
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if (result == COMPACT_SKIPPED)
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if (result == COMPACT_SKIPPED)
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return true;
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return true;
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return false;
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}
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/*
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* Compaction has backed off for some reason after doing some work or none
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* at all. It might be throttling or lock contention. Retrying might be still
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* worthwhile, but with a higher priority if allowed.
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*/
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static inline bool compaction_withdrawn(enum compact_result result)
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{
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/*
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/*
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* If compaction is deferred for high-order allocations, it is
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* If compaction is deferred for high-order allocations, it is
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* because sync compaction recently failed. If this is the case
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* because sync compaction recently failed. If this is the case
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@ -207,6 +214,11 @@ static inline bool compaction_failed(enum compact_result result)
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return false;
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return false;
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}
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}
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static inline bool compaction_needs_reclaim(enum compact_result result)
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{
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return false;
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}
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static inline bool compaction_withdrawn(enum compact_result result)
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static inline bool compaction_withdrawn(enum compact_result result)
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{
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{
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return true;
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return true;
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@ -3955,16 +3955,24 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
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goto check_priority;
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goto check_priority;
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/*
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/*
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* make sure the compaction wasn't deferred or didn't bail out early
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* compaction was skipped because there are not enough order-0 pages
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* due to locks contention before we declare that we should give up.
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* to work with, so we retry only if it looks like reclaim can help.
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* But do not retry if the given zonelist is not suitable for
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* compaction.
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*/
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*/
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if (compaction_withdrawn(compact_result)) {
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if (compaction_needs_reclaim(compact_result)) {
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ret = compaction_zonelist_suitable(ac, order, alloc_flags);
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ret = compaction_zonelist_suitable(ac, order, alloc_flags);
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goto out;
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goto out;
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}
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}
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/*
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* make sure the compaction wasn't deferred or didn't bail out early
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* due to locks contention before we declare that we should give up.
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* But the next retry should use a higher priority if allowed, so
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* we don't just keep bailing out endlessly.
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*/
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if (compaction_withdrawn(compact_result)) {
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goto check_priority;
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}
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/*
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/*
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* !costly requests are much more important than __GFP_RETRY_MAYFAIL
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* !costly requests are much more important than __GFP_RETRY_MAYFAIL
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* costly ones because they are de facto nofail and invoke OOM
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* costly ones because they are de facto nofail and invoke OOM
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