Re: 3.1-rc2: CONFIG_NUMA Question

[Justin Piszcz]

On Thu, 18 Aug 2011, AmÃrico Wang wrote:

> On Thu, Aug 18, 2011 at 6:51 PM, Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > I have a SuperMicro X8DTH-6F motherboard with 2 cpus it has NUMA options in
> > the BIOS; what parameters/should I be using for the NUMA options in the
> > kernel?
> >
> > Â| |  Â[*] Numa Memory Allocation and Scheduler Support         | |
> > Â| |  Â[ ] Old style AMD Opteron NUMA detection             | |
> > Â| |  Â[*] ACPI NUMA detection                     Â| |
> > Â| |  Â[ ] NUMA emulation                        | |
> > Â| | Â Â(6) Maximum NUMA Nodes (as a power of 2) Â Â Â Â Â Â Â Â Â Â Â Â | |
>
> That is Intel processor, right? If so, the things you selected here are enough,
Hi, yes-- two Intel Xeon E5645s.

> the rest two is not what you need.
Ok.

> > Specifically, the maximum number of NUMA nodes? ÂWill this help to increase
> > performance of large memory allocations/is there any downside
> > to enabling this feature?
>
> The max of NUMA nodes is specified by CONFIG_NODES_SHIFT,
> in your case, it is 6, which means it supports up to 2^6 nodes.
Ok, is there any overhead having more than is needed?

> If your hardware supports NUMA, yes, that certainly help to increase
> the performance.
Nice, thanks.

Justin.