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    SubjectRe: Unresponiveness of 2.4.16
    On Tue, Nov 27 2001, Andrew Morton wrote:
    > Jens Axboe wrote:
    > >
    > > I agree that the current i/o scheduler has really bad interactive
    > > performance -- at first sight your changes looks mostly like add-on
    > > hacks though.
    > Good hacks, or bad ones?
    > It keeps things localised. It works. It's tunable. It's the best
    > IO scheduler presently available.

    Hacks look ok on cursory glances :-)

    > > Arjan's priority based scheme is more promising.
    > If the IO priority becomes an attribute of the calling process
    > then an approach like that has value. For writes, the priority
    > should be driven by VM pressure and it's probably simpler just
    > to stick the priority into struct buffer_head -> struct request.
    > For reads, the priority could just be scooped out of *current.
    > If we're not going to push the IO priority all the way down from
    > userspace then you may as well keep the logic inside the elevator
    > and just say reads-go-here and writes-go-there.

    Priority will be passed down for reads as you suggest, at least that is
    the intention I had as well. I've only worked on 2.5 with this, but I
    guess we can find some space in the buffer_head to squeeze in some
    priority bits.

    > But this has potential to turn into a great designfest. Are

    Oh yeah

    > we going to leave 2.4 as-is? Please say no.

    I'd be happy to review anything you come up with -- or in other works,
    feel free to knock yourself out, I'm busy with other stuff currently :)

    Jens Axboe

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