Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()

[Rik van Riel]

On 01/07/2010 12:36 PM, Linus Torvalds wrote:
> On Thu, 7 Jan 2010, Peter Zijlstra wrote:
> > Right, supposing we can make this speculative fault stuff work, then we
> > can basically reduce the mmap_sem usage in fault to:
> >
> >    - allocating new page tables
> >    - extending the growable vmas
> >
> > And do everything else without holding it, including zeroing and IO.
>
> Well, I have yet to hear a realistic scenario of _how_ to do it all
> speculatively in the first place, at least not without horribly subtle
> complexity issues. So I'd really rather see how far we can possibly get by
> just improving mmap_sem.

I would like to second this sentiment.  I am trying to make the
anon_vma and rmap bits more scalable for multi-process server
workloads and it is quite worrying how complex locking already
is.

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