From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757309AbZKMPTC (ORCPT ); Fri, 13 Nov 2009 10:19:02 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757275AbZKMPSi (ORCPT ); Fri, 13 Nov 2009 10:18:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:21527 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755948AbZKMPSf (ORCPT ); Fri, 13 Nov 2009 10:18:35 -0500 Date: Fri, 13 Nov 2009 10:18:15 -0500 From: Vivek Goyal To: Corrado Zoccolo Cc: linux-kernel@vger.kernel.org, jens.axboe@oracle.com, nauman@google.com, dpshah@google.com, lizf@cn.fujitsu.com, ryov@valinux.co.jp, fernando@oss.ntt.co.jp, s-uchida@ap.jp.nec.com, taka@valinux.co.jp, guijianfeng@cn.fujitsu.com, jmoyer@redhat.com, balbir@linux.vnet.ibm.com, righi.andrea@gmail.com, m-ikeda@ds.jp.nec.com, akpm@linux-foundation.org, riel@redhat.com, kamezawa.hiroyu@jp.fujitsu.com Subject: Re: [PATCH 05/16] blkio: Implement per cfq group latency target and busy queue avg Message-ID: <20091113151815.GC17076@redhat.com> References: <1258068756-10766-1-git-send-email-vgoyal@redhat.com> <1258068756-10766-6-git-send-email-vgoyal@redhat.com> <4e5e476b0911130246m372eb8e8x7b98f13278515a95@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4e5e476b0911130246m372eb8e8x7b98f13278515a95@mail.gmail.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 13, 2009 at 11:46:49AM +0100, Corrado Zoccolo wrote: > On Fri, Nov 13, 2009 at 12:32 AM, Vivek Goyal wrote: > >  static inline void > > @@ -441,10 +445,13 @@ cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) > >        if (cfqd->cfq_latency) { > >                /* interested queues (we consider only the ones with the same > >                 * priority class) */ > This comment needs to be updated Sure. Will do. Now the interested queues are the one with same priority class with-in group. > >                 * priority class) */ > > -               unsigned iq = cfq_get_avg_queues(cfqd, cfq_class_rt(cfqq)); > > +               unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg, > > +                                               cfq_class_rt(cfqq)); > >                unsigned sync_slice = cfqd->cfq_slice[1]; > >                unsigned expect_latency = sync_slice * iq; > > -               if (expect_latency > cfq_target_latency) { > > +               unsigned group_target_lat = cfq_target_latency/cfqd->nr_groups; > > I'm not sure that we should divide the target latency evenly among groups. > Groups with different weights will have different percentage of time > in each 300ms round, so probably we should consider it here. > Taking group weight into account will be more precise thing. So may be I can keep track of total weight on the service tree and determine group target latency as proportion of total weight. group_target_lat = group_weight * cfq_target_latency/total_weight_of_groups Thanks Vivek > > + > > +               if (expect_latency > group_target_lat) { > >                        unsigned base_low_slice = 2 * cfqd->cfq_slice_idle; > >                        /* scale low_slice according to IO priority > >                         * and sync vs async */ > > @@ -452,7 +459,7 @@ cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) > >                                min(slice, base_low_slice * slice / sync_slice); > >                        /* the adapted slice value is scaled to fit all iqs > >                         * into the target latency */ > > -                       slice = max(slice * cfq_target_latency / expect_latency, > > +                       slice = max(slice * group_target_lat / expect_latency, > >                                    low_slice); > >                } > >        } > > Thanks, > Corrado