On Thu, Oct 13, 2016 at 12:59:14PM +0200, Vlastimil Babka wrote: > On 10/13/2016 10:08 AM, js1304@xxxxxxxxx wrote: > >From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > > >Allocation/free pattern is usually sequantial. If they are freed to > >the buddy list, they can be coalesced. However, we first keep these freed > >pages at the pcp list and try to reuse them until threshold is reached > >so we don't have enough chance to get a high order freepage. This reusing > >would provide us some performance advantages since we don't need to > >get the zone lock and we don't pay the cost to check buddy merging. > >But, less fragmentation and more high order freepage would compensate > >this overhead in other ways. First, we would trigger less direct > >compaction which has high overhead. And, there are usecases that uses > >high order page to boost their performance. > > > >Instantly resuing freed page seems to provide us computational benefit > >but the other affects more precious things like as I/O performance and > >memory consumption so I think that it's a good idea to weight > >later advantage more. > > Again, there's also cache hotness to consider. And whether the > sequential pattern is still real on a system with higher uptime. > Should be possible to evaluate with tracepoints? I answered this in previous e-mail. Anyway, we should evaluate cache-effect. tracepoint or perf's cache event would show some evidence. I will do it soon and report again. Thanks. -- 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>