On Tue, May 12, 2015 at 10:36:40AM +0200, Vlastimil Babka wrote: > On 04/27/2015 09:23 AM, Joonsoo Kim wrote: > >Sometimes we try to get more freepages from buddy list than how much > >we really need, in order to refill pcp list. This may speed up following > >allocation request, but, there is a possibility to increase fragmentation > >if we steal freepages from other migratetype buddy list excessively. This > >patch changes this behaviour to stop fallback allocation in order to > >reduce fragmentation if we already get some freepages. > > > >CPU: 8 > >RAM: 512 MB with zram swap > >WORKLOAD: kernel build with -j12 > >OPTION: page owner is enabled to measure fragmentation > >After finishing the build, check fragmentation by 'cat /proc/pagetypeinfo' > > > >* Before > >Number of blocks type (movable) > >DMA32: 208.4 > > > >Number of mixed blocks (movable) > >DMA32: 139 > > > >Mixed blocks means that there is one or more allocated page for > >unmovable/reclaimable allocation in movable pageblock. Results shows that > >more than half of movable pageblock is tainted by other migratetype > >allocation. > > > >* After > >Number of blocks type (movable) > >DMA32: 207 > > > >Number of mixed blocks (movable) > >DMA32: 111.2 > > > >This result shows that non-mixed block increase by 38% in this case. > > > >Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > I agree that keeping fragmentation low is more important than > filling up the pcplists. Wouldn't expect such large difference > though. Are the results stable? Yes, I think that improvement is very stable. stdev is roughly 8 in 5 runs. 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>