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    SubjectRe: [RESEND][RFC] BFQ I/O Scheduler
    > From: Jens Axboe <jens.axboe@oracle.com>
    > Date: Thu, Apr 17, 2008 11:27:55AM +0200
    >
    > On Thu, Apr 17 2008, Paolo Valente wrote:
    > > Maybe there is also another middle-ground solution. I'll try to sketch
    ...
    > > Does it seem reasonable?
    >
    > Not for CFQ, that will stay time based. The problem with #2 above is
    > that it then quickly turns to various heuristics, which is just
    > impossible to tune for general behaviour. Or it just falls apart for
    > other real life situations.
    >

    Ok.

    After a brief offline discussion with paolo, here it is what we can do:

    o propose a patch for discussion that uses our WF2Q+ variant to
    schedule timeslices in cfq. The resulting scheduler would be
    quite close to the EEVDF scheduler discussed some time ago for
    the cpu.

    o Introduce a timeout in bfq to give an upper time limit to the
    slices. Since we have not experimented with that mixed approach
    before[*], we will need to do some tests with relevant workloads to
    see if/how it can work.

    I fear that it will take some time, as we're both travelling in this
    week.

    [*] Anyway it is quite close to how cfq handles async queues, with their
    slice_async and slice_async_rq, so it's definitely not something new.


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