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

Peter Zijlstra
2007-03-16T10:36:30Z

On Fri, 2007-03-16 at 11:30 +0100, Eric Dumazet wrote:
> 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 ...

I though the cacheline was 128 bytes, but point taken.