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    SubjectRe: IO Priorities
    On Mon, Dec 13 2004, Jeff Sipek wrote:
    > On Mon, Dec 13, 2004 at 03:38:10PM +0100, Jens Axboe wrote:
    > > On Mon, Dec 13 2004, Jeff Sipek wrote:
    > > > Hello all,
    > > > About a week ago, I said I would try to implement IO priorities.
    > > > I tried. I got the whole thing done, but there is one major problem - it
    > >
    > > I did too, did you see my patch?
    >
    > I did after I sent mine. I was reading it and I noticed:
    >
    > "Disable TCQ in the hardware/driver by default. Can be changed (as
    > always) with the max_depth setting. If you do that, don't expect
    > fairness or priorities to work as well."
    >
    > Would this cause my problem?

    Only if you test on SCSI with TCQ enabled. But I already outlined what
    your problems are even if you did.

    > > Additionally, you don't do anything with the priorities internally.
    >
    > Sure I do, I multiply the slice by cfq_prio_scale[ioprio]. It did seem
    > too simple. :-) Looking at your code right now, I kind of see some code
    > that should have been in my implementation as well. Back to coding...
    > :-)

    If you would base changes on what I already did with CFQ, that would be
    handy. You need the CFQ bits anyways.

    Updated patch here:

    http://www.kernel.org/pub/linux/kernel/people/axboe/patches/v2.6/2.6.10-rc3-mm1/cfq-time-slices-11-2.6.10-rc3-mm1.gz

    --
    Jens Axboe

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