On Thu, Sep 29, 2016 at 03:14:33PM +0900, Joonsoo Kim wrote: > On Wed, Sep 28, 2016 at 10:25:40PM -0400, Johannes Weiner wrote: > > On Wed, Sep 28, 2016 at 11:39:25AM -0400, Johannes Weiner wrote: > > > On Wed, Sep 28, 2016 at 11:00:15AM +0200, Vlastimil Babka wrote: > > > > I guess testing revert of 9c0415e could give us some idea. Commit > > > > 3a1086f shouldn't result in pageblock marking differences and as I said > > > > above, 99592d5 should be just restoring to what 3.10 did. > > > > > > I can give this a shot, but note that this commit makes only unmovable > > > stealing more aggressive. We see reclaimable blocks up as well. > > > > Quick update, I reverted back to stealing eagerly only on behalf of > > MIGRATE_RECLAIMABLE allocations in a 4.6 kernel: > > Hello, Johannes. > > I think that it would be better to check 3.10 with above patches. > Fragmentation depends on not only policy itself but also > allocation/free pattern. There might be a large probability that > allocation/free pattern is changed in this large kernel version > difference. You mean backport suspicious patches to 3.10 until I can reproduce it there? I'm not sure. You're correct, the patterns very likely *have* changed. But that alone cannot explain mobility grouping breaking that badly. There is a reproducable bad behavior. It should be easier to track down than to try to recreate it in the last-known-good kernel. > > This is an UNMOVABLE order-3 allocation falling back to RECLAIMABLE. > > According to can_steal_fallback(), this allocation shouldn't steal the > > pageblock, yet change_ownership=1 indicates the block is UNMOVABLE. > > > > Who converted it? I wonder if there is a bug in ownership management, > > and there was an UNMOVABLE block on the RECLAIMABLE freelist from the > > beginning. AFAICS we never validate list/mt consistency anywhere. > > According to my code review, it would be possible. When stealing > happens, we moved those buddy pages to current requested migratetype > buddy list. If the other migratetype allocation request comes and > stealing from the buddy list of previous requested migratetype > happens, change_ownership will show '1' even if there is no ownership > changing. These two paths should exclude each other through the zone->lock, no? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>