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    SubjectRe: REGRESSION: Performance regressions from switching anon_vma->lock to mutex
    On Fri, Jun 17, 2011 at 11:39 AM, Linus Torvalds
    <torvalds@linux-foundation.org> wrote:
    >
    > Having gone over it a bit more, I actually think I prefer to just
    > special-case the allocation instead.

    Just to explain my thinking: the thing I disliked most about doing an
    allocation while holding the lock wasn't that I thought we would
    deadlock on page reclaim. I don't claim that kind of far-sight.

    No, the thing I disliked was that if we're low on memory and actually
    have to wait, I disliked having the lack of concurrency. I'm ok with
    holding the mutex over a few more CPU cycles, but anything longer
    might actually hurt throughput. So the patch I just sent out should
    fix both the page reclaim deadlock, and avoid any problems with delays
    due to holding the critical lock over an expensive allocation.

    Linus


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