From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753783Ab2LQWND (ORCPT ); Mon, 17 Dec 2012 17:13:03 -0500 Received: from mail-pb0-f46.google.com ([209.85.160.46]:35303 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752253Ab2LQWNA (ORCPT ); Mon, 17 Dec 2012 17:13:00 -0500 Date: Mon, 17 Dec 2012 14:12:54 -0800 From: Tejun Heo To: Vivek Goyal Cc: lizefan@huawei.com, axboe@kernel.dk, containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, ctalbott@google.com, rni@google.com Subject: Re: [PATCH 07/12] cfq-iosched: implement hierarchy-ready cfq_group charge scaling Message-ID: <20121217221254.GH1844@htj.dyndns.org> References: <1355524885-22719-1-git-send-email-tj@kernel.org> <1355524885-22719-8-git-send-email-tj@kernel.org> <20121217205317.GI7235@redhat.com> <20121217211738.GD1844@htj.dyndns.org> <20121217212736.GB13691@redhat.com> <20121217213314.GF1844@htj.dyndns.org> <20121217214911.GC13691@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121217214911.GC13691@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey, Vivek. On Mon, Dec 17, 2012 at 04:49:11PM -0500, Vivek Goyal wrote: > > Eh? Then how would it compete with the children cfqgs? You can > > consider it as the hidden leaf node competing with the children cfqgs, > > right? So, you take the leaf weight and divide it by the total active > > weight of all the children (including the hidden leaf node). It isn't > > different from the rest of the calculation. It just looks different > > because leaf_weight is stored elsewhere and we look down there and > > then walke up. The calculation being done is exactly the same one. > > Again it is coming from multiplexing cfqg and cfqg->task_group. So > effectively we are calculating the vfraction of task_group inside cfqg. Or calculating the fraction of the hidden leaf node. > Once you say cfqg->vfraction, I immediately think of total share of > group (including task_group and all children cgroups). Any tasks should be treated as member of the hidden leaf node, so... > May be cfqg->task_group_vfraction (or cfqg->tg_fraction) is a better name. I don't know. Wouldn't just explaining clearly in the comment e enough? I think the name "vfraction" is already weird enough to indicate that it's something which you need to read explanation about. If that explanation is readily available as comment, I think it should be okay. > Also descrition says. > > /* vfraction the fraction of vdisktime that a cfqg is entitled to */ > > May be we can clarify it that it is share of task_group of cfqg. Yeah, no objection. Let's beef up the explanation there. > I guess i am too familiar with how cpu has done it. I think I am getting > confused with properties which belong to cfqg and properties which > belong to cfqg->task_group. > > I guess if we prefix fields belong to task_group with somete suitable > string, it might become little easier to understand. I usually am not a big fan of adding wordy prefixes. I think they tend to obfuscate/frustrate more than help. Let's stick a weird (that is, non-generic) name to something weird and explain it well in the comment. Thanks. -- tejun