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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>
This commit is contained in:
Vlastimil Babka 2019-09-23 15:37:32 -07:00 committed by Linus Torvalds
parent 5ee04716c4
commit 4943308556
2 changed files with 30 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
include/linux/compaction.h
View File

@ -129,11 +129,8 @@ static inline bool compaction_failed(enum compact_result result)
return false;
}
/*
* Compaction has backed off for some reason. It might be throttling or
* lock contention. Retrying is still worthwhile.
*/
static inline bool compaction_withdrawn(enum compact_result result)
/* Compaction needs reclaim to be performed first, so it can continue. */
static inline bool compaction_needs_reclaim(enum compact_result result)
{
/*
* Compaction backed off due to watermark checks for order-0
@ -142,6 +139,16 @@ static inline bool compaction_withdrawn(enum compact_result result)
if (result == COMPACT_SKIPPED)
return true;
return false;
}
/*
* Compaction has backed off for some reason after doing some work or none
* at all. It might be throttling or lock contention. Retrying might be still
* worthwhile, but with a higher priority if allowed.
*/
static inline bool compaction_withdrawn(enum compact_result result)
{
/*
* If compaction is deferred for high-order allocations, it is
* because sync compaction recently failed. If this is the case
@ -207,6 +214,11 @@ static inline bool compaction_failed(enum compact_result result)
return false;
}
static inline bool compaction_needs_reclaim(enum compact_result result)
{
return false;
}
static inline bool compaction_withdrawn(enum compact_result result)
{
return true;

18
mm/page_alloc.c
View File

@ -3955,16 +3955,24 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
goto check_priority;
/*
* 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.
* 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_withdrawn(compact_result)) {
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 the next retry should use a higher priority if allowed, so
* we don't just keep bailing out endlessly.
*/
if (compaction_withdrawn(compact_result)) {
goto check_priority;
}
/*
* !costly requests are much more important than __GFP_RETRY_MAYFAIL
* costly ones because they are de facto nofail and invoke OOM