From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755311AbZBZK3I (ORCPT ); Thu, 26 Feb 2009 05:29:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753096AbZBZK2z (ORCPT ); Thu, 26 Feb 2009 05:28:55 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:55439 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbZBZK2y (ORCPT ); Thu, 26 Feb 2009 05:28:54 -0500 Message-ID: <18f6db017e5d44596e828e0753f28e75.squirrel@webmail-b.css.fujitsu.com> In-Reply-To: <344eb09a0902260210y44c0684by9b22f041116d3f7c@mail.gmail.com> References: <49A6475F.4000502@cn.fujitsu.com> <20090226170738.a982057b.kamezawa.hiroyu@jp.fujitsu.com> <49A6501B.7040604@cn.fujitsu.com> <20090226172234.a931931f.kamezawa.hiroyu@jp.fujitsu.com> <49A65455.4030204@cn.fujitsu.com> <20090226174033.094e4834.kamezawa.hiroyu@jp.fujitsu.com> <344eb09a0902260210y44c0684by9b22f041116d3f7c@mail.gmail.com> Date: Thu, 26 Feb 2009 19:28:45 +0900 (JST) Subject: Re: [PATCH] cpuacct: add a branch prediction From: "KAMEZAWA Hiroyuki" To: "Bharata B Rao" Cc: "KAMEZAWA Hiroyuki" , "Li Zefan" , "Ingo Molnar" , "Peter Zijlstra" , "Paul Menage" , "Balbir Singh" , "LKML" User-Agent: SquirrelMail/1.4.16 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-2022-jp Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) Importance: Normal Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bharata B Rao： > On Thu, Feb 26, 2009 at 2:10 PM, KAMEZAWA Hiroyuki > wrote: >> On Thu, 26 Feb 2009 16:35:33 +0800 >> Li Zefan wrote: >> >>> ca is not checked before hierarchy support, and it's a side-effect. >>> >>> Before cpuacct is initialized, css == >>> task->cgroups->subsys[cpuacct_subsys] == NULL, >>> but ca = task_ca(tsk) is not necessarily NULL, unless struct >>> cgroup_subsys_state is the >>> first member of struct cpuacct. >>> >>> And the above code actually should be: >>> >>> do { >>>       ... >>> } while (ca->parent); >>> >> I'll send no more objections to this patch itself. >> >> But IMHO, this loop is tooo bad, I think. The hierarchy information >> should be gathered by >> read-side and the total code should be > > How do you take care of accounting when a group gets deleted ?. propagate accounts to the parent or root group if deleted. > Wouldn't you loose some information due to deleted groups if you want > to accumulate hierarchical stats only during read ? > Taking hierarchy mutex while reading will make read-side stable. I haven't considered in detail but I wrote CSS ID and scan hierarchy code to do this kind of "visit all css object under hierarchy" jobs. I think you can catch what I mean by reading what memory.stat file of mem cgroup does. (mmotm) Thanks, -Kame