Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932182Ab0GUTlF (ORCPT ); Wed, 21 Jul 2010 15:41:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59262 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758869Ab0GUTk7 (ORCPT ); Wed, 21 Jul 2010 15:40:59 -0400 From: Jeff Moyer To: Vivek Goyal Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk, nauman@google.com, dpshah@google.com, guijianfeng@cn.fujitsu.com, czoccolo@gmail.com Subject: Re: [PATCH 2/3] cfq-iosched: Implement a tunable group_idle References: <1279739181-24482-1-git-send-email-vgoyal@redhat.com> <1279739181-24482-3-git-send-email-vgoyal@redhat.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Wed, 21 Jul 2010 15:40:44 -0400 In-Reply-To: <1279739181-24482-3-git-send-email-vgoyal@redhat.com> (Vivek Goyal's message of "Wed, 21 Jul 2010 15:06:20 -0400") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1830 Lines: 51 Vivek Goyal writes: > o Implement a new tunable group_idle, which allows idling on the group > instead of a cfq queue. Hence one can set slice_idle = 0 and not idle > on the individual queues but idle on the group. This way on fast storage > we can get fairness between groups at the same time overall throughput > improves. > > Signed-off-by: Vivek Goyal > --- [snip] > @@ -1929,13 +1941,21 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd) > return; > } > > + /* There are other queues in the group, don't do group idle */ > + if (group_idle && cfqq->cfqg->nr_cfqq > 1) > + return; > + > cfq_mark_cfqq_wait_request(cfqq); > > - sl = cfqd->cfq_slice_idle; > + if (group_idle) > + sl = cfqd->cfq_group_idle; > + else > + sl = cfqd->cfq_slice_idle; What happens when both group_idle and slice_idle are set? Is that a sane thing to do from a user's perspective? If not, please protect against it in the configuration code. If so, then explain why we prefer group_idle here, but slice_idle in completed request for the extend_sl: > @@ -3425,7 +3458,10 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq) > * the queue. > */ > if (cfq_should_wait_busy(cfqd, cfqq)) { > - cfqq->slice_end = jiffies + cfqd->cfq_slice_idle; > + unsigned long extend_sl = cfqd->cfq_slice_idle; > + if (!cfqd->cfq_slice_idle) > + extend_sl = cfqd->cfq_group_idle; > + cfqq->slice_end = jiffies + extend_sl; Also, you'll need to add documentation for this new tunable. Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/