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Re: How about NUMA?

On Wed, 8 Jul 2009 21:49:00 -0600
lee <lee@yun.yagibdah.de> wrote:

> Hi,
> under what circumstances are you supposed to turn on NUMA support in
> the kernel settings? I've googled about that and learned what NUMA is
> about while trying to answer the question wheather I should enable it
> in my kernel or not. But I couldn't find the answer I was looking for.
> Do Intel DualCores (E8400) support NUMA? Do you need special hardware,
> like a special mainboard supporting NUMA, to benefit from this
> feature? Do these CPUs support NUMA? It seems to me that leaving it
> disabled is better in my case, and the kernel help also says that it's
> probably better not to enable it if you don't have more than two
> CPUs/cores.
> Now if I had a quad core CPU instead, would I better enable NUMA? Or
> if I had an AMD instead of Intel, would I turn it on? Or should I
> leave it turned on?

A good first answer is that if you don't know what NUMA is then you don't need
it. If you want a more precise answer what NUMA is:

NUMA = non uniform memory access. It means that each cpu connects directly to
it's local memory and slowly (via some communication channel) to other memory.
The closest you would get with a desktop box (which I don't think is possible
yet) would be with a dual CPU core i7 (note, dual cpu, not dual core), since
corei7 has it's own memory controller. Core 2 duo connects via the north side
bus and thus even with two CPUs they still connect to the same memory via the
north side bus. If you have a multi CPU opetron system they also are NUMA

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