On 2014-04-08 09:17:04 -0500, Christoph Lameter wrote: > On Tue, 8 Apr 2014, Vlastimil Babka wrote: > > > On 04/08/2014 12:34 AM, Mel Gorman wrote: > > > When it was introduced, zone_reclaim_mode made sense as NUMA distances > > > punished and workloads were generally partitioned to fit into a NUMA > > > node. NUMA machines are now common but few of the workloads are NUMA-aware > > > and it's routine to see major performance due to zone_reclaim_mode being > > > disabled but relatively few can identify the problem. > > ^ I think you meant "enabled" here? > > > > Just in case the cover letter goes to the changelog... > > Correct. > > Another solution here would be to increase the threshhold so that > 4 socket machines do not enable zone reclaim by default. The larger the > NUMA system is the more memory is off node from the perspective of a > processor and the larger the hit from remote memory. FWIW, I've the problem hit majorly on 8 socket machines. Those are the largest I have seen so far in postgres scenarios. Everything larger is far less likely to be used as single node database server, so that's possibly a sensible cutoff. But then, I'd think that special many-socket machines are setup by specialists, that'd know to enable if it makes sense... Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- 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>