From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx205.postini.com [74.125.245.205]) by kanga.kvack.org (Postfix) with SMTP id 6680B6B0027 for ; Wed, 20 Mar 2013 04:18:54 -0400 (EDT) Date: Wed, 20 Mar 2013 09:18:51 +0100 From: Michal Hocko Subject: Re: [PATCH v2 2/5] memcg: provide root figures from system totals Message-ID: <20130320081851.GG20045@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> <20130320080347.GE20045@dhcp22.suse.cz> <51496E71.5010707@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51496E71.5010707@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 12:08:17, Glauber Costa wrote: > On 03/20/2013 12:03 PM, Michal Hocko wrote: > > 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? > > > Of course not, but the whole point here is *not* accounting root. I thought the objective was to not account root if there are no children. I would see the "not account root at all" as another step. And we are skipping charging it already (do not call mem_cgroup_do_charge) for root. > So if we are entirely skipping root account, it, I personally believe > we need to replace it with something else so we can keep things > working as much as we can. > > It doesn't need to be perfect, though: There is no way we can have > max_usage without something like a res_counter that locks memory > charges. I believe we can live without that. But as for the basic > statistics and numbers, I believe they should keep working. [...] -- 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