Re: [2.6 patch] i386: always use 4k stacks

Oliver Neukum
2005-12-16T19:14:20Z

Am Freitag, 16. Dezember 2005 20:02 schrieb Arjan van de Ven:
>
> >
> > So what about arches where single-page stacks aren't viable (for example
> > x86_64)? Are we just screwed?
>
>
> x86 is specially handicapped due to the fact that the stacks need to be
> in the lowmem zone. Even if you have 8Gb ram, the lowmem zone is still
> 800Mb and a bit, and this gets to be under a high pressure, like
> hyper-fragmentation. Same for bounce buffers etc etc.
>
> note that the order thing is by far not the only advantage, pure memory
> usage alone and cache locality also are wins. The memory usage halves
> for kernel stacks after all (which means you can do more threads in
> java, or use the memory for disk cache ;)

1. Cache usage depends on actual stack usage. How much you allocate
doesn't matter
2. You are surely getting a cache effect by using interrupt stacks. Which
is larger?
3. When you use kmalloc instead of the stack you are reducing locality.

Regards
Oliver