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    SubjectRe: [PATCH 0/2] pdflush fix and enhancement
    On Wed, 2008-12-31 at 14:27 +0100, Andi Kleen wrote:
    > > I say most because the assumption would be that we will be successful in
    > > creating the new thread. Not that bad an assumption I think. Besides,
    > And that the memory read is not reordered (rmb()).

    At the risk of showing my b*tt here... I'm not very clear on memory
    barriers, is this necessary even inside a critical region? (recall
    we're protected by the spin lock). If so, does the barrier go after the
    read, or before? (Thanks for not laughing, however grins are allowed)

    > Ok it probably needs some kind of feedback mechanism.

    Actually, I tend to think we need an entirely different approach to
    flushing, please see my post to David Chinner which outlines some
    thoughts. Basically a flushing heuristic that takes into account the
    characteristics of the various block devices.

    > >
    > > I was thinking about a patch that would go both directions - forward and
    > > reverse depending upon, say, a bit in jiffies... Certainly not perfect,
    > > but a bit more fair.
    > Better a real RNG. But such probalistic schemes unfortunately tend to drive
    > benchmarkers crazy, that is why it is better to avoid them.

    Nod, but that's ok. Having been one for several years I can truthfully
    say that benchmarkers are a little crazy anyways... :-)

    > I suppose you could just keep some state per fs to ensure fairness.

    Nod, this would be ideal.


    > -Andi

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