On Thu, Mar 31, 2016 at 10:50:36AM +0200, Vlastimil Babka wrote: > The goal of direct compaction is to quickly make a high-order page available > for the pending allocation. The free page scanner can add significant latency > when searching for migration targets, although to succeed the compaction, the > only important limit on the target free pages is that they must not come from > the same order-aligned block as the migrated pages. >
What prevents the free pages being allocated from behind the migration scanner? Having compaction abort when the scanners meet misses compaction opportunities but it avoids the problem of Compactor A using pageblock X as a migration target and Compactor B using pageblock X as a migration source. -- Mel Gorman SUSE Labs
