From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751752Ab0JYBGc (ORCPT ); Sun, 24 Oct 2010 21:06:32 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:63454 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751407Ab0JYBGb (ORCPT ); Sun, 24 Oct 2010 21:06:31 -0400 Message-ID: <4CC4D84C.5000705@cn.fujitsu.com> Date: Mon, 25 Oct 2010 09:07:24 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1b3pre) Gecko/20090513 Fedora/3.0-2.3.beta2.fc11 Thunderbird/3.0b2 MIME-Version: 1.0 To: Peter Zijlstra CC: "akpm >> Andrew Morton" , Paul Menage , Stephane Eranian , LKML , containers@lists.linux-foundation.org Subject: Re: [PATCH 0/7] cgroups: Allow to bind/unbind subsystems to/from non-trival hierarchy References: <4CC146A4.9090505@cn.fujitsu.com> <1287751801.15336.35.camel@twins> In-Reply-To: <1287751801.15336.35.camel@twins> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra wrote: > On Fri, 2010-10-22 at 16:09 +0800, Li Zefan wrote: >> Stephane posted a patchset to add perf_cgroup subsystem, so perf can >> be used to monitor all threads belonging to a cgroup. >> >> But if you already mounted a cgroup hierarchy but without perf_cgroup >> and the hierarchy has sub-cgroups, you can't bind perf_cgroup to it, >> and thus you're not able to use per-cgroup perf feature. >> >> This patchset alleviates the pain, and then a subsytem can be >> bound/unbound to/from a hierarchy which has sub-cgroups in it. >> >> Some subsystems still can't take advantage of this patchset, memcgroup >> and cpuset in specific. >> >> For cpuset, if a hierarchy has a sub-cgroup and the cgroup has tasks, >> we can't decide sub-cgroup's cpuset.mems and cpuset.cpus automatically >> if we try to bind cpuset to this hierarchy. >> >> For memcgroup, memcgroup uses css_get/put(), and due to some complexity, >> for now bindable subsystems should not use css_get/put(). >> >> Usage: >> >> # mount -t cgroup -o cpuset xxx /mnt >> # mkdir /mnt/tmp >> # echo $$ > /mnt/tmp/tasks >> >> (add cpuacct to the hierarchy) >> # mount -o remount,cpuset,cpuacct xxx /mnt >> >> (remove it from the hierarchy) >> # mount -o remount,cpuset xxx /mnt >> >> There's another limitation, cpuacct should not be bound to any mounted >> hierarchy before the above operation. But that's not a problem, as you >> can remove it from a hierarchy and bind it to another one. > > Right, so the only remaining problem I see with this approach is that > you cannot profile two different hierarchies at the same time, but I > can't really think of a solution to that problem (nor do I care very > much). > Paul had a patch to allow some subsystems to be added to multi-hierarchies, which may help. But it forbids accessing t->cgroups, which makes this feature of limited use. Anyway I too don't care much about this. > Seems like a nice approach, Thanks Li! > Thanks!