Re: [PATCH 0/3] FUTEX : new PRIVATE futexes, SMP and NUMA improvements

[Eric Dumazet]

On Friday 16 March 2007 11:10, Peter Zijlstra wrote:

> http://programming.kicks-ass.net/kernel-patches/futex-vma-cache/vma_cache.p
>atch

Oh thanks

>
> > But if it has to walk the vmas (and take mmap_sem), you already loose the
> > PRIVATE benefit.
>
> It doesn't take mmap_sem, I am aware of the problems.

Yes but the vma_anon() -> vma_cache_find() needs to read 3 cache lines on 
x86_64 (sizeof(struct vma_cache) = 136)
and dirty one bit, so it might be more expensive than the mmap_sem ...

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