Re: [rfc 08/45] cpu alloc: x86 support

Christoph Lameter
2007-11-20T02:14:22Z

On Mon, 19 Nov 2007, H. Peter Anvin wrote:

> You're making the assumption here that NUMA = large number of CPUs. This
> assumption is flat-out wrong.

Well maybe. Usually one gets to NUMA because the hardware gets too big to
be handleed the UMA way.

> On x86-64, most two-socket systems are still NUMA, and I would expect that
> most distro kernels probably compile in NUMA. However,
> burning megabytes of memory on a two-socket dual-core system when we're
> talking about tens of kilobytes used would be more than a wee bit insane.

Yeah yea but the latencies are minimal making the NUMA logic too expensive
for most loads ... If you put a NUMA kernel onto those then performance
drops (I think someone measures 15-30%?)