From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755013Ab0JHAsH (ORCPT ); Thu, 7 Oct 2010 20:48:07 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:49885 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752162Ab0JHAsF (ORCPT ); Thu, 7 Oct 2010 20:48:05 -0400 Message-ID: <4CAE69E5.5080007@cn.fujitsu.com> Date: Fri, 08 Oct 2010 08:46:29 +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: Stephane Eranian CC: eranian@gmail.com, linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@elte.hu, paulus@samba.org, davem@davemloft.net, fweisbec@gmail.com, perfmon2-devel@lists.sf.net, robert.richter@amd.com, acme@redhat.com Subject: Re: [RFC PATCH 1/2] perf_events: add support for per-cpu per-cgroup monitoring (v4) References: <4cac3d2e.21edd80a.7008.1831@mx.google.com> <4CAD206A.1090708@cn.fujitsu.com> In-Reply-To: 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 >>>> +#ifdef CONFIG_CGROUPS >>>> +struct perf_cgroup_time { >>>> + u64 time; >>>> + u64 timestamp; >>>> +}; >>>> + >>>> +struct perf_cgroup { >>>> + struct cgroup_subsys_state css; >>>> + struct perf_cgroup_time *time; >>>> +}; >>> Can we avoid adding this perf cgroup subsystem? It has 2 disavantages: >>> >> Well, I need to maintain some timing information for each cgroup. This has >> to be stored somewhere. >> Seems you can simply store it in struct perf_event? >>> - If one mounted cgroup fs without perf cgroup subsys, he can't monitor it. >> That's unfortunately true ;-) >> >>> - If there are several different cgroup mount points, only one can be >>> monitored. >>> >>> To choose which cgroup hierarchy to monitor, hierarchy id can be passed >>> from userspace, which is the 2nd column below: >>> >> Ok, I will investigate this. As long as the hierarchy id is unique AND it can be >> searched, then we can use it. Using /proc is fine with me. >> >>> $ cat /proc/cgroups >>> #subsys_name hierarchy num_cgroups enabled >>> debug 0 1 1 >>> net_cls 0 1 1 >>> > > If I mount all subsystems: > mount -t cgroup none /dev/cgroup > Then, I get: > #subsys_name hierarchy num_cgroups enabled > cpuset 1 1 1 > cpu 1 1 1 > perf_event 1 1 1 > > In other words, the hierarchy id is not unique. > If the perf_event is not mounted, then hierarchy id = 0. > Yes, it's unique. ;) You mounted them together, and that's a cgroup hierarchy, so they have the same hierarchy id. If you mount them seperately: # mount -t cgroup -o debug xxx /cgroup1 # mount -t cgroup -o net_cls xxx /cgroup2/ # cat /proc/cgroups #subsys_name hierarchy num_cgroups enabled debug 1 1 1 net_cls 2 1 1 They now have different hierarchy id, because they belong to different cgroup hierarchy. So pid + hierarchy_id locates the cgroup. > When I compare with my approach, if perf_event is > not mounted, then the file descriptor won't lead to the > css, and therefore you will fail and that is fine because > it means the perf_event subsystem is not instantiated > therefore it cannot be used. > > In my patch, there was a missing check for a NULL > css. I fixed that now, and it works fine. > > As for multiple mount points, it seems like the first > mount determines the restrictions for all mounts. > In other words, if you mount only cpuset, then no > other mount can provide more than cpuset, and vice-versa. > > I have tried mounting cgroupfs in multiple places at the same > time. Whatever directory I used, I got to the right css. > > Am I missing your point here? > I should use the words "cgroup hierarchies" instead of mount points..