From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756803AbZLNLBT (ORCPT ); Mon, 14 Dec 2009 06:01:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756790AbZLNLBQ (ORCPT ); Mon, 14 Dec 2009 06:01:16 -0500 Received: from mail-yx0-f187.google.com ([209.85.210.187]:51839 "EHLO mail-yx0-f187.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756788AbZLNLBP convert rfc822-to-8bit (ORCPT ); Mon, 14 Dec 2009 06:01:15 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=HFEsjrbR3zJn4O4+3vHgRfqT3WbiUUh6jV2nHTED0CSUfgydA1SB8V2BtABhIopzgA zloEgShS00nI71FGKGCGMBolfDn9Zouo6i1Bas8WowcyTbwqWiXXCwPO3n38trAC1KsZ rshSK2485Wg1BQe1gCMO702eYEovqT0e+p53E= MIME-Version: 1.0 In-Reply-To: <4B260B72.9020204@cn.fujitsu.com> References: <4B21D252.1060902@cn.fujitsu.com> <20091211150727.GB2756@redhat.com> <4e5e476b0912111001h3c0b9798u2a2b25c9fcc39504@mail.gmail.com> <20091211184630.GA7066@redhat.com> <4B25A4F0.60407@cn.fujitsu.com> <4e5e476b0912140039s2f802786t84f53ee62b87c04e@mail.gmail.com> <4B260B72.9020204@cn.fujitsu.com> Date: Mon, 14 Dec 2009 12:01:14 +0100 Message-ID: <4e5e476b0912140301x398ac2b7k5ab7fc5698b9675e@mail.gmail.com> Subject: Re: [PATCH] cfq: Take whether cfq group is changed into account when choosing service tree From: Corrado Zoccolo To: Gui Jianfeng Cc: Vivek Goyal , Jens Axboe , linux kernel mailing list Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gui, On Mon, Dec 14, 2009 at 10:54 AM, Gui Jianfeng wrote: > Corrado Zoccolo wrote: >> Hi, > Currently, IIUC, only the workload that didn't use up its slice will be saved, and only > such workloads are restoring when a group is resumed. So sometimes, we'll still get the > previous serving_type and workload_expires. Am i missing something? You are right. cfq_choose_cfqg should set the workload as expired if !cfqg->saved_workload_slice (just set cfqd->workload_expires = jiffies - 1), so the workload will be chosen again as the lowest keyed one. Can you send a patch to fix this? > > >> >> I have one more concern, though. >> RT priority has now changed meaning. Before, an RT task would always >> have priority access to the disk. Now, a BE task in a different group, >> with lower weight, can steal the disk from the RT task. >> A way to preserve the old meaning is to consider wheter a group has RT >> tasks inside when sorting groups tree, and putting those groups at the >> front. >> Usually, RT tasks will be put in the root group, and this (if >> group_isolation=0) will automatically make sure that also the noidle >> workload gets serviced quickly after RT tasks release the disk. We >> could even enforce that, with group_isolation=0, all RT tasks are put >> in the root group. >> >> The rationale behind this suggestion is that groups are for user >> processes, while RT is system wide, since it is only root that can >> grant it. > >  I agree, and one more thing, currently we can't see fairness between different >  idle tasks in different groups. Because we only allow idle cfqq dispatch one request >  for its dispatch round even if it's the only task in the cgroup, group always loose it >  share. So whether we can rely on group_isolation, when group_isolation == 1 we provide >  isolation for idle tasks. Agreed. Thanks, Corrado > > Thanks > Gui > > >