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Subject: Re: [PATCH 0/3] FUTEX : new PRIVATE futexes, SMP and NUMA
	improvements
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>, Ulrich Drepper <drepper@gmail.com>,
       Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>,
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       "Shai Fultheim (Shai@scalex86.org)" <shai@scalex86.org>,
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Date: Fri, 16 Mar 2007 11:36:26 +0100
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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.