tree f45ed33dd41fe1b5cea7b4b966d90ef79e9a8363
parent c2033b00dbe856909fcaccf038e4e0d3dcfb85af
author Vlastimil Babka <vbabka@suse.cz> 1475884837 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1475891189 -0700

mm, compaction: make full priority ignore pageblock suitability

Several people have reported premature OOMs for order-2 allocations
(stack) due to OOM rework in 4.7.  In the scenario (parallel kernel
build and dd writing to two drives) many pageblocks get marked as
Unmovable and compaction free scanner struggles to isolate free pages.
Joonsoo Kim pointed out that the free scanner skips pageblocks that are
not movable to prevent filling them and forcing non-movable allocations
to fallback to other pageblocks.  Such heuristic makes sense to help
prevent long-term fragmentation, but premature OOMs are relatively more
urgent problem.  As a compromise, this patch disables the heuristic only
for the ultimate compaction priority.

Link: http://lkml.kernel.org/r/20160906135258.18335-5-vbabka@suse.cz
Reported-by: Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@quantum.com>
Reported-by: Arkadiusz Miskiewicz <a.miskiewicz@gmail.com>
Reported-by: Olaf Hering <olaf@aepfle.de>
Suggested-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>