Re: [PATCH 14/20] mm: Remove i_mmap_lock lockbreak

[Andrew Morton]

On Fri, 01 Apr 2011 14:13:12 +0200
Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:

> Hugh says:
>  "The only significant loser, I think, would be page reclaim (when
>   concurrent with truncation): could spin for a long time waiting for
>   the i_mmap_mutex it expects would soon be dropped? "
> 
> Counter points:
>  - cpu contention makes the spin stop (need_resched())
>  - zap pages should be freeing pages at a higher rate than reclaim
>    ever can
> 
> I think the simplification of the truncate code is definately worth it.

Well, we don't need to guess.  These things are testable!
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