lkml.org 
[lkml]   [2005]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
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.

Justin
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:09    [from the cache]
©2003-2011 Jasper Spaans