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Date: Fri, 15 Jan 2010 21:24:23 +0100 From: Corrado Zoccolo <czoccolo@...il.com> To: Jeff Moyer <jmoyer@...hat.com> Cc: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>, Shaohua Li <shaohua.li@...el.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "jens.axboe@...cle.com" <jens.axboe@...cle.com>, "Zhang, Yanmin" <yanmin.zhang@...el.com> Subject: Re: [PATCH]cfq-iosched: don't take requests with long distence as close On Fri, Jan 15, 2010 at 8:45 PM, Jeff Moyer <jmoyer@...hat.com> wrote: > Corrado Zoccolo <czoccolo@...il.com> writes: > >> Hi Jeff, >> I think this patch has the same flaw as Shaohua's. >> The seekiness check that you introduce in cfq_rq_close is already >> present in its caller, cfq_close_cooperator, so it is not effective. > > I don't think so. There are two queues, here. One queue is checked by > the caller, and that is the cur_cfqq. The __cfqq needs to also be > checked. The other one, i.e. the returned one, is also checked by the caller, some lines below. 1756 cfqq = cfqq_close(cfqd, cur_cfqq); 1757 if (!cfqq) 1758 return NULL; 1759 1760 /* If new queue belongs to different cfq_group, don't choose it */ 1761 if (cur_cfqq->cfqg != cfqq->cfqg) 1762 return NULL; 1763 1764 /* 1765 * It only makes sense to merge sync queues. 1766 */ 1767 if (!cfq_cfqq_sync(cfqq)) 1768 return NULL; 1769 if (CFQQ_SEEKY(cfqq)) 1770 return NULL; > >> Up to now, the only patch that improves this situation is the one that >> changes the unmerge policy to unmerge after a single time slice. > > Yes, I definitely agree with that, and I think that patch should go in. > > Cheers, > Jeff > -- __________________________________________________________________________ dott. Corrado Zoccolo mailto:czoccolo@...il.com PhD - Department of Computer Science - University of Pisa, Italy -------------------------------------------------------------------------- The self-confidence of a warrior is not the self-confidence of the average man. The average man seeks certainty in the eyes of the onlooker and calls that self-confidence. The warrior seeks impeccability in his own eyes and calls that humbleness. Tales of Power - C. Castaneda -- 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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