From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx189.postini.com [74.125.245.189]) by kanga.kvack.org (Postfix) with SMTP id C4D3E6B0068 for ; Fri, 30 Nov 2012 09:59:31 -0500 (EST) Received: by mail-pb0-f41.google.com with SMTP id xa7so509591pbc.14 for ; Fri, 30 Nov 2012 06:59:31 -0800 (PST) Date: Fri, 30 Nov 2012 06:59:24 -0800 From: Tejun Heo Subject: Re: [PATCHSET cgroup/for-3.8] cpuset: decouple cpuset locking from cgroup core Message-ID: <20121130145924.GA3873@htj.dyndns.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50B883B5.8020705@parallels.com> Sender: owner-linux-mm@kvack.org List-ID: To: Glauber Costa 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 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. Thanks. -- tejun -- 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