From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx132.postini.com [74.125.245.132]) by kanga.kvack.org (Postfix) with SMTP id F19F66B0002 for ; Wed, 20 Mar 2013 04:33:33 -0400 (EDT) Message-ID: <51497479.30701@parallels.com> Date: Wed, 20 Mar 2013 12:34:01 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH v2 2/5] memcg: provide root figures from system totals 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> <20130320081851.GG20045@dhcp22.suse.cz> In-Reply-To: <20130320081851.GG20045@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko 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 03/20/2013 12:18 PM, Michal Hocko wrote: > 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. It is the goal, yes. As I said: I want the root-only case to keep providing userspace with meaningful statistics, therefore the bypass. But since the machinery is in place, it is trivial to keep bypassing for use_hierarchy = 1 at the root level. If you believe it would be simpler, I could refrain from doing 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