On Wed 02-03-16 11:55:07, Joonsoo Kim wrote: > On Tue, Mar 01, 2016 at 07:14:08PM +0100, Vlastimil Babka wrote: [...] > > Yes, compaction is historically quite careful to avoid making low > > memory conditions worse, and to prevent work if it doesn't look like > > it can ultimately succeed the allocation (so having not enough base > > pages means that compacting them is considered pointless). This > > aspect of preventing non-zero-order OOMs is somewhat unexpected :) > > It's better not to assume that compaction would succeed all the times. > Compaction has some limitations so it sometimes fails. > For example, in lowmem situation, it only scans small parts of memory > and if that part is fragmented by non-movable page, compaction would fail. > And, compaction would defer requests 64 times at maximum if successive > compaction failure happens before. > > Depending on compaction heavily is right direction to go but I think > that it's not ready for now. More reclaim would relieve problem.
I really fail to see why. The reclaimable memory can be migrated as well, no? Relying on the order-0 reclaim makes only sense to get over wmarks. -- Michal Hocko SUSE Labs
