On Tue 18-02-14 14:27:11, David Rientjes wrote: > On Tue, 18 Feb 2014, Michal Hocko wrote: > > > Hi, > > I have just noticed that ppc has RECLAIM_DISTANCE reduced to 10 set by > > 56608209d34b (powerpc/numa: Set a smaller value for RECLAIM_DISTANCE to > > enable zone reclaim). The commit message suggests that the zone reclaim > > is desirable for all NUMA configurations. > > > > History has shown that the zone reclaim is more often harmful than > > helpful and leads to performance problems. The default RECLAIM_DISTANCE > > for generic case has been increased from 20 to 30 around 3.0 > > (32e45ff43eaf mm: increase RECLAIM_DISTANCE to 30). > > > > I strongly suspect that the patch is incorrect and it should be > > reverted. Before I will send a revert I would like to understand what > > led to the patch in the first place. I do not see why would PPC use only > > LOCAL_DISTANCE and REMOTE_DISTANCE distances and in fact machines I have > > seen use different values. > > > > I strongly suspect that the patch is correct since powerpc node distances > are different than the architectures you're talking about and get doubled > for every NUMA domain that the hardware supports. Even if the units of the distance is different on PPC should every NUMA machine have zone_reclaim enabled? That doesn't right to me. -- Michal Hocko SUSE Labs -- 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>