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SubjectRe: [RESEND][RFC] BFQ I/O Scheduler
> From: Jens Axboe <>
> 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.


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

[*] 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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