On 06/28/2012 09:28 AM, Rik van Riel wrote: > On 06/27/2012 07:59 PM, Minchan Kim wrote: > >> I doubt compaction try to migrate continuously although we have no >> free memory. >> Could you apply this patch and retest? >> >> https://lkml.org/lkml/2012/6/21/30 > > Another possibility is that compaction is succeeding every time, > but since we always start scanning all the way at the beginning > and end of each zone, we waste a lot of CPU time rescanning the > same pages (that we just filled up with moved pages) to see if > any are free. It does make sense. > > In short, due to the way compaction behaves right now, > compaction + isolate_freepages are essentially quadratic. > > What we need to do is remember where we left off after a > successful compaction, so we can continue the search there > at the next invocation. > Good idea. It could enhance parallel compaction, too. Of course, if we can't meet the goal, we need loop around from start/end of zone. -- Kind regards, Minchan Kim -- 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>