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Date: Thu, 17 Apr 2008 11:24:14 +0200 From: Paolo Valente <paolo.valente@...more.it> To: Jens Axboe <jens.axboe@...cle.com> CC: Pavel Machek <pavel@....cz>, linux-kernel@...r.kernel.org Subject: Re: [RESEND][RFC] BFQ I/O Scheduler Jens Axboe ha scritto: > > > I was thinking about that too. Generally I've been opposed to doing > scheduling decisions on anything but time, since that is always > relevant. When to hand out slices and to what process, that algorithm is > really basic in CFQ and could do with an improvement. > > Maybe there is also another middle-ground solution. I'll try to sketch it out: . use sectors instead of time . impose a penalty to each thread in proportion to the distance between its disk requests . reduce the maximum budget of each thread as a function of this seek penalty so as to prevent the thread from stealing more than a given time slice (the simple mechanism to limit per-thread budget is already implemented in bfq). By doing so, both fairness and time isolation should be guaranteed. Finally, this policy should be safe in that, given the maximum time used by a seeky thread to consume its maximum budget on a reference disk, the time used on any faster disk should be shorter. Does it seem reasonable? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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