Re: Which dual opteron?

From: Brian Hall (brihall_at_nowhere.org)
Date: 10/08/04 

Date: Fri, 08 Oct 2004 17:15:50 -0000

On 2004-10-08, Anton Ertl wrote:
> Chris Cox <ccox_nopenotthis@airmail.net> writes:
>>Al Dykes wrote:
>>...
>>>
>>> All opeterons are numa architecture.
>>
>>Well... the cheaper dual boards use a shared bus to a common
>>bank of memory so in the spirit of numa.. I'd say I don't
>>think so. The higher end boards are the ones with the
>>separate banks for each processor. Perhaps the shared
>>bus is still numa somehow??
>
> Certainly a single process can see different (i.e., non-uniform)
> memory access times on such machines, although now at different times
> (if the scheduler changes the CPU of the process) rather than for
> different memory areas.
>
> The consequences for the software are simpler than for normal NUMAs
> (the scheduler should prefer one CPU when only one process is ready),
> but normal NUMA optimizations (allocate memory close to the process
> and schedule the process close to its memory) should also degenerate
> to this simpler policy on such a machine.

So on a board that does this (like my MSI K8T Master2 FAR), should I
enable NUMA or not in the kernel config? If there is no advantage to
doing so, I would think it might be better to leave it disabled, since
the NUMA code path is less used/tested. 

--
Brian Hall
Linux Consultant
http://pcisys.net/~brihall

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