From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx126.postini.com [74.125.245.126]) by kanga.kvack.org (Postfix) with SMTP id BBC766B0002 for ; Wed, 20 Mar 2013 04:03:52 -0400 (EDT) Date: Wed, 20 Mar 2013 09:03:47 +0100 From: Michal Hocko Subject: Re: [PATCH v2 2/5] memcg: provide root figures from system totals Message-ID: <20130320080347.GE20045@dhcp22.suse.cz> References: <1362489058-3455-1-git-send-email-glommer@parallels.com> <1362489058-3455-3-git-send-email-glommer@parallels.com> <20130319124650.GE7869@dhcp22.suse.cz> <20130319125509.GF7869@dhcp22.suse.cz> <51495F35.9040302@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51495F35.9040302@parallels.com> Sender: owner-linux-mm@kvack.org List-ID: To: Glauber Costa Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, Tejun Heo , Andrew Morton , kamezawa.hiroyu@jp.fujitsu.com, handai.szj@gmail.com, anton.vorontsov@linaro.org, Johannes Weiner , Mel Gorman On Wed 20-03-13 11:03:17, Glauber Costa wrote: > On 03/19/2013 04:55 PM, Michal Hocko wrote: > > On Tue 19-03-13 13:46:50, Michal Hocko wrote: > >> On Tue 05-03-13 17:10:55, Glauber Costa wrote: > >>> For the root memcg, there is no need to rely on the res_counters if hierarchy > >>> is enabled The sum of all mem cgroups plus the tasks in root itself, is > >>> necessarily the amount of memory used for the whole system. Since those figures > >>> are already kept somewhere anyway, we can just return them here, without too > >>> much hassle. > >>> > >>> Limit and soft limit can't be set for the root cgroup, so they are left at > >>> RESOURCE_MAX. Failcnt is left at 0, because its actual meaning is how many > >>> times we failed allocations due to the limit being hit. We will fail > >>> allocations in the root cgroup, but the limit will never the reason. > >> > >> I do not like this very much to be honest. It just adds more hackery... > >> Why cannot we simply not account if nr_cgroups == 1 and move relevant > >> global counters to the root at the moment when a first group is > >> created? > > > > OK, it seems that the very next patch does what I was looking for. So > > why all the churn in this patch? > > Why do you want to make root even more special? > > Because I am operating under the assumption that we want to handle that > transparently and keep things working. If you tell me: "Hey, reading > memory.usage_in_bytes from root should return 0!", then I can get rid of > that. If you simply switch to accounting for root then you do not have to care about this, don't you? > The fact that I keep bypassing when hierarchy is present, it is > more of a reuse of the infrastructure since it's there anyway. > > Also, I would like the root memcg to be usable, albeit cheap, for > projects like memory pressure notifications. root memcg without any childre, right? -- Michal Hocko SUSE Labs -- 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