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

[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 ;)

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