Re: [patch 05/14] percpu: Use a Kconfig variable to configure arch specific percpu setup

Jeremy Fitzhardinge
2007-11-29T01:55:12Z

Christoph Lameter wrote:
> The percpu areas need to be allocated in a NUMA aware fashion. Otherwise
> you use distant memory for the most performance sensitive areas. The NUMA
> subsystem must be so far up that these allocations can be performed in the
> right way. And this means at least you need to know on which node each
> processor is located. That is what the PDA is currently used for and i386
> has no other way of doing that. I think we could use an array [NR_CPUS]
> for this one but we want to avoid these arrays because NR_CPUS may get
> very big.
>

Oh, you mean there needs to be some percpu data mechanism operating in
order to do numa-aware allocations, which would be necessary to allocate
the percpu memory itself?

I can see how that would be awkward.

J