From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx172.postini.com [74.125.245.172]) by kanga.kvack.org (Postfix) with SMTP id 92DD06B00B5 for ; Fri, 30 Nov 2012 10:10:09 -0500 (EST) Message-ID: <50B8CC3D.3040901@parallels.com> Date: Fri, 30 Nov 2012 19:09:49 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCHSET cgroup/for-3.8] cpuset: decouple cpuset locking from cgroup core References: <1354138460-19286-1-git-send-email-tj@kernel.org> <50B8263C.7060908@jp.fujitsu.com> <50B875B4.2020507@parallels.com> <20121130092435.GD29317@dhcp22.suse.cz> <50B87F84.7040206@parallels.com> <20121130094959.GE29317@dhcp22.suse.cz> <50B883B5.8020705@parallels.com> <20121130145924.GA3873@htj.dyndns.org> In-Reply-To: <20121130145924.GA3873@htj.dyndns.org> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Michal Hocko , Kamezawa Hiroyuki , lizefan@huawei.com, paul@paulmenage.org, containers@lists.linux-foundation.org, cgroups@vger.kernel.org, peterz@infradead.org, bsingharora@gmail.com, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 11/30/2012 06:59 PM, Tejun Heo wrote: > Hello, > > On Fri, Nov 30, 2012 at 02:00:21PM +0400, Glauber Costa wrote: >> Now, what I am actually seeing with cgroup creation, is that the >> children will copy a lot of the values from the parent, like swappiness, >> hierarchy, etc. Once the child copies it, we should no longer be able to >> change those values in the parent: otherwise we'll get funny things like >> parent.use_hierarchy = 1, child.use_hierarchy = 0. > > So, the best way to do this is from ->css_online(). If memcg > synchronizes and inherits from ->css_online(), it can guarantee that > the new cgroup will be visible in any following iterations. Just have > an online flag which is turned on and off from ->css_on/offline() and > ignore any cgroups w/o online set. > >> One option is to take a global lock in memcg_alloc_css(), and keep it >> locked until we did all the cgroup bookkeeping, and then unlock it in >> css_online. But I am guessing Tejun won't like it very much. > > No, please *NEVER* *EVER* do that. You'll be creating a bunch of > locking dependencies as cgroup walks through different controllers. > > memcg should be able to synchornize fully both css on/offlining and > task attachments in memcg proper. Let's please be boring about > locking. > Of course, there was a purely rhetorical statement, as indicated by "Tejun won't like it very much" =p Take a look at the final result, I just posted a couple of hours ago. Let me know if there is still something extremely funny, and I'll look into fixing it. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org