[lkml]   [2005]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: NUMA or not on dual Opteron
On Thu, Jan 13, 2005 at 11:02:19AM +0100, Raphael Jacquot wrote:
> >I was under the impression that NUMA is useful on > 2-way systems only.
> >Is this true, and if not, under what circumstances is NUMA useful on
> >2-way Opteron systems?
> >
> >In other words: why should one want NUMA to be enabled or disabled for
> >dual Opteron?
> >
> >Thanks in advance.
> >
> Numa needs to be enabled on bi-opteron systems because each processor
> controls part of the memory. unlike the intel memory architecture, where
> processors share the same bus to access memory.
> Numa in opteron systems is thus required to allow sharing of memory .

This is somewhat true. There are 2 types of dual opteron boards. Those in
the $200 US range only have one memory bank, which is attached to CPU0.
They operate as a single node, and may perform better with numa turned off.
Those in the $400+ range tend to have one bank per CPU and will certainly
perform better with numa on. They do usually have a bios option to
interleave the nodes which would show up as a single node, and probably
perform better with numa turned off, but a better solution is to turn off
the node interleave in bios and run the kernel with numa support.
Basically if you have 2 CPUs and only one memory bank, maybe turning numa
off will give better performance, but if you have one memory bank per CPU
numa should be on.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 14:09    [W:0.157 / U:0.400 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site