Re: [PATCH] x86_64: Make NR_IRQS configurable in Kconfig

Andrew Morton
2006-08-08T02:42:07Z

On Tue, 8 Aug 2006 04:17:59 +0200
Andi Kleen <ak@suse.de> wrote:

>
> >
> > And it's a pretty nasty one because it can get people into the situation
> > where the kernel worked fine for those who released it, but users who
> > happen to load more modules (or the right combination of them) will
> > experience per-cpu memory exhaustion.
>
> Yes, and a high value will waste a lot of memory for normal users.
>
> > So shouldn't we being scaling the per-cpu memory as well?
>
> If we move it into vmalloc space it would be easy to extend at runtime - just the
> virtual address space would need to be prereserved, but then more pages
> could be mapped. Maybe we should just do that instead of continuing to kludge around?

Sounds sane.

otoh, we need something for 2.6.19.

> Drawback would be some more TLB misses.

yup. On some (important) architectures - I'm not sure which architectures
do the bigpage-for-kernel trick.