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    SubjectRe: [PATCH 03/10] writeback: stop background writeback when below background threshold
    On Fri, Sep 25, 2009 at 12:26:00AM +0800, Peter Zijlstra wrote:
    > On Thu, 2009-09-24 at 18:13 +0200, Jens Axboe wrote:
    >
    > > > > > for (;;) {
    > > > > > /*
    > > > > > + * Stop writeback when nr_pages has been consumed
    > > > > > */
    > > > > > + if (args->nr_pages <= 0)
    > > > > > break;
    > > > > >
    > > > > > /*
    > > > > > + * For background writeout, stop when we are below the
    > > > > > + * background dirty threshold
    > > > > > */
    > > > > > + if (args->for_background && !over_bground_thresh())
    > > > > > break;
    > > > >
    > > > >
    > > > > What I'm not getting is why this is conditional on for_background(),
    > > > > shouldn't we always stop writeback when below the background threshold?
    > > >
    > > > Ah, that would be for things like sync, which need to write out
    > > > everything, right?

    Besides sync, it's reasonable for periodic writeback to write all
    inodes as long as they are expired.

    > > Yes, wb_writeback() handles any kind of writeback. The definition of our
    > > background writeout is to stop when we are no longer over the background
    > > writeout threshold.
    >
    > Right, ok
    >
    > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

    Thanks! This patch was partly inspired by your comments :)

    Regards,
    Fengguang


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