Re: Dual Opteron box, what's the optimal memory placement for the CPUs?

[Petr Vandrovec]

On Thu, Oct 28, 2004 at 12:00:45AM +0200, Jesper Juhl wrote:

> Yeah, I know they have to be installed in pairs, but I would have thought 
> that it would be best to have an even memory distribution so that an even 
> amount of local memory was available to processes executing on either CPU. 
> Even if Linux makes sure to execute processes on the CPU where most of 
> their memory is local, wouldn't a non-even distribution make more 
> processes prefer one CPU and thus not make the best possible use of them?
> 
> I don't really know very much about this specific detail (which is why I 
> asked), and you tell me it doesn't matter, so I'll assume Linux has some 
> intelligent way of dealing with this that I just don't know about - That's 
> good enough for me, I'll trust you on that, just wanted to know for now 
> and the future. :-)

You should also check this with your BIOS.  It will be a bit unfortunate 
if BIOS decides to just throw away 0.5GB of your memory to make space
for PCI devices, and maybe you can help BIOS a bit with right
shuffling (with 3:1 it will hopefully decide to put 1GB above
4GB boundary; with 2:2 who knows; AFAIK Opteron northbridge does not
allow for splitting DRAM on one node into two regions; at least I did not 
found how to do that).

I would prefer 2:2 if both variants give you same amount of accessible
memory.
						Best regards,
							Petr Vandrovec
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