From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757355AbZEVMfW (ORCPT ); Fri, 22 May 2009 08:35:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753453AbZEVMfK (ORCPT ); Fri, 22 May 2009 08:35:10 -0400 Received: from mx2.redhat.com ([66.187.237.31]:38448 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751319AbZEVMfJ (ORCPT ); Fri, 22 May 2009 08:35:09 -0400 Date: Fri, 22 May 2009 08:32:31 -0400 From: Vivek Goyal To: Gui Jianfeng Cc: nauman@google.com, dpshah@google.com, lizf@cn.fujitsu.com, mikew@google.com, fchecconi@gmail.com, paolo.valente@unimore.it, jens.axboe@oracle.com, ryov@valinux.co.jp, fernando@oss.ntt.co.jp, s-uchida@ap.jp.nec.com, taka@valinux.co.jp, jmoyer@redhat.com, dhaval@linux.vnet.ibm.com, balbir@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, righi.andrea@gmail.com, agk@redhat.com, dm-devel@redhat.com, snitzer@redhat.com, m-ikeda@ds.jp.nec.com, akpm@linux-foundation.org Subject: Re: [PATCH 02/18] io-controller: Common flat fair queuing code in elevaotor layer Message-ID: <20090522123231.GA14972@redhat.com> References: <1241553525-28095-1-git-send-email-vgoyal@redhat.com> <1241553525-28095-3-git-send-email-vgoyal@redhat.com> <4A164978.1020604@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A164978.1020604@cn.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 22, 2009 at 02:43:04PM +0800, Gui Jianfeng wrote: > Vivek Goyal wrote: > ... > > +/* A request got completed from io_queue. Do the accounting. */ > > +void elv_ioq_completed_request(struct request_queue *q, struct request *rq) > > +{ > > + const int sync = rq_is_sync(rq); > > + struct io_queue *ioq = rq->ioq; > > + struct elv_fq_data *efqd = &q->elevator->efqd; > > + > > + if (!elv_iosched_fair_queuing_enabled(q->elevator)) > > + return; > > + > > + elv_log_ioq(efqd, ioq, "complete"); > > + > > + elv_update_hw_tag(efqd); > > + > > + WARN_ON(!efqd->rq_in_driver); > > + WARN_ON(!ioq->dispatched); > > + efqd->rq_in_driver--; > > + ioq->dispatched--; > > + > > + if (sync) > > + ioq->last_end_request = jiffies; > > + > > + /* > > + * If this is the active queue, check if it needs to be expired, > > + * or if we want to idle in case it has no pending requests. > > + */ > > + > > + if (elv_active_ioq(q->elevator) == ioq) { > > + if (elv_ioq_slice_new(ioq)) { > > + elv_ioq_set_prio_slice(q, ioq); > > Hi Vivek, > > Would you explain a bit why slice_end should be set when first request completes. > Why not set it just when an ioq gets active? > Hi Gui, I have kept the behavior same as CFQ. I guess reason behind this is that when a new queue is scheduled in, first request completion might take more time as head of the disk might be quite a distance away (due to previous queue) and one probably does not want to charge the new queue for that first seek time. That's the reason we start the queue slice when first request has completed. Thanks Vivek