Commit d20bdd57 authored by Zi Yan's avatar Zi Yan Committed by Linus Torvalds

mm/compaction: stop isolation if too many pages are isolated and we have pages to migrate

In isolate_migratepages_block, if we have too many isolated pages and
nr_migratepages is not zero, we should try to migrate what we have
without wasting time on isolating.

In theory it's possible that multiple parallel compactions will cause
too_many_isolated() to become true even if each has isolated less than
COMPACT_CLUSTER_MAX, and loop forever in the while loop.  Bailing
immediately prevents that.

[vbabka@suse.cz: changelog addition]

Fixes: 1da2f328 (“mm,thp,compaction,cma: allow THP migration for CMA allocations”)
Suggested-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarZi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Yang Shi <shy828301@gmail.com>
Link: https://lkml.kernel.org/r/20201030183809.3616803-2-zi.yan@sent.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 38935861
......@@ -817,6 +817,10 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* delay for some time until fewer pages are isolated
*/
while (unlikely(too_many_isolated(pgdat))) {
/* stop isolation if there are still pages not migrated */
if (cc->nr_migratepages)
return 0;
/* async migration should just abort */
if (cc->mode == MIGRATE_ASYNC)
return 0;
......
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