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Date: Wed, 21 Oct 2009 12:36:49 -0400 From: Jeff Moyer <jmoyer@...hat.com> To: Corrado Zoccolo <czoccolo@...il.com> Cc: Linux-Kernel <linux-kernel@...r.kernel.org>, Jens Axboe <jens.axboe@...cle.com> Subject: Re: [RFC V2 PATCH 1/5] cfq-iosched: adapt slice to number of processes doing I/O Corrado Zoccolo <czoccolo@...il.com> writes: >> Couldn't you have just divided the slice by iq? And why iq? Why not >> nr_qs or avg_qlen or something? It's a minor nit; I can live with it. > > iq stands for interested queues, because we are restricting the count > just to the same priority class, not all queues in the system. Ah, that makes sense. A comment would make that clear. > I don't think this is equivalent. You seem to compute some divisions > too early, losing in precision. OK, I figured as much. > slice * cfq_target_latency / (cfqd->cfq_slice[1] * iq) > is not generally equivalent to: > slice * (cfq_target_latency / (cfqd->cfq_slice[1] * iq)) > that is what you are computing. > There is an other such case in your simplification. OK. The idea was to try to make the thing a bit more digestable. Honestly, I had to re-write it to figure out what it was doing. Could you rework it so the logic is more obvious to others and still correct? Thanks! Jeff -- 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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