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    SubjectRe: [PATCH 18/45] writeback: introduce wait queue for balance_dirty_pages()
    On Thu, 08 Oct 2009 10:08:36 +0200
    Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

    > On Thu, 2009-10-08 at 09:58 +0800, Wu Fengguang wrote:
    > >
    > > > How this runqueue->nr_iowait is handled now ?
    > >
    > > Good question. io_schedule() has an old comment for throttling IO wait:
    > >
    > > * But don't do that if it is a deliberate, throttling IO wait (this task
    > > * has set its backing_dev_info: the queue against which it should throttle)
    > > */
    > > void __sched io_schedule(void)
    > >
    > > So it looks both Jens' and this patch behaves right in ignoring the
    > > iowait accounting for balance_dirty_pages() :)
    >
    > Well it is a change in behaviour, and I think IOWAIT makes sense when
    > we're blocked due to io throttle..
    >
    > Hmm?
    >
    Above comment "don't do that if it is a deliberate, throttling IO wait" is
    really old but ignored.
    I pesonally don't like to change the meanig of iowait in /proc/stat.
    But I'm not sure which is better to change the definitiion (which was ignored) or
    fix behavior (not correct very long time)...

    Hmm?, too ;)

    Regards,
    -Kame



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