* KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> [2010-10-08 10:48:26]: > Recently, Robert Mueller reported zone_reclaim_mode doesn't work > properly on his new NUMA server (Dual Xeon E5520 + Intel S5520UR MB). > He is using Cyrus IMAPd and it's built on a very traditional > single-process model. > > * a master process which reads config files and manages the other > process > * multiple imapd processes, one per connection > * multiple pop3d processes, one per connection > * multiple lmtpd processes, one per connection > * periodical "cleanup" processes. > > Then, there are thousands of independent processes. The problem is, > recent Intel motherboard turn on zone_reclaim_mode by default and > traditional prefork model software don't work fine on it. > Unfortunatelly, Such model is still typical one even though 21th > century. We can't ignore them. > > This patch raise zone_reclaim_mode threshold to 30. 30 don't have > specific meaning. but 20 mean one-hop QPI/Hypertransport and such > relatively cheap 2-4 socket machine are often used for tradiotional > server as above. The intention is, their machine don't use > zone_reclaim_mode. > > Note: ia64 and Power have arch specific RECLAIM_DISTANCE definition. > then this patch doesn't change such high-end NUMA machine behavior. > > Cc: Mel Gorman <mel@xxxxxxxxx> > Cc: Bron Gondwana <brong@xxxxxxxxxxx> > Cc: Robert Mueller <robm@xxxxxxxxxxx> > Acked-by: Christoph Lameter <cl@xxxxxxxxx> > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > --- > include/linux/topology.h | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/include/linux/topology.h b/include/linux/topology.h > index 64e084f..bfbec49 100644 > --- a/include/linux/topology.h > +++ b/include/linux/topology.h > @@ -60,7 +60,7 @@ int arch_update_cpu_topology(void); > * (in whatever arch specific measurement units returned by node_distance()) > * then switch on zone reclaim on boot. > */ > -#define RECLAIM_DISTANCE 20 > +#define RECLAIM_DISTANCE 30 > #endif > #ifndef PENALTY_FOR_NODE_WITH_CPUS > #define PENALTY_FOR_NODE_WITH_CPUS (1) I am not sure if this makes sense, since RECLAIM_DISTANCE is supposed to be a hardware parameter. Could you please help clarify what the access latency of a node with RECLAIM_DISTANCE 20 to that of a node with RECLAIM_DISTANCE 30 is? Has the hardware definition of reclaim distance changed? I suspect the side effect is the zone_reclaim_mode is not set to 1 on bootup for the 2-4 socket machines you mention, which results in better VM behaviour? -- Three Cheers, Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>