From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754548Ab2HON0Z (ORCPT ); Wed, 15 Aug 2012 09:26:25 -0400 Received: from cantor2.suse.de ([195.135.220.15]:47433 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751920Ab2HON0X (ORCPT ); Wed, 15 Aug 2012 09:26:23 -0400 Date: Wed, 15 Aug 2012 15:26:21 +0200 From: Michal Hocko To: Glauber Costa Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, devel@openvz.org, Johannes Weiner , Andrew Morton , kamezawa.hiroyu@jp.fujitsu.com, Christoph Lameter , David Rientjes , Pekka Enberg Subject: Re: [PATCH v2 04/11] kmem accounting basic infrastructure Message-ID: <20120815132621.GJ23985@dhcp22.suse.cz> References: <1344517279-30646-1-git-send-email-glommer@parallels.com> <1344517279-30646-5-git-send-email-glommer@parallels.com> <20120814162144.GC6905@dhcp22.suse.cz> <502B6D03.1080804@parallels.com> <20120815123931.GF23985@dhcp22.suse.cz> <502B9BD4.4070003@parallels.com> <20120815130228.GH23985@dhcp22.suse.cz> <502B9E5F.2080907@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <502B9E5F.2080907@parallels.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 15-08-12 17:04:31, Glauber Costa wrote: > On 08/15/2012 05:02 PM, Michal Hocko wrote: > > On Wed 15-08-12 16:53:40, Glauber Costa wrote: > > [...] > >>>>> This doesn't check for the hierachy so kmem_accounted might not be in > >>>>> sync with it's parents. mem_cgroup_create (below) needs to copy > >>>>> kmem_accounted down from the parent and the above needs to check if this > >>>>> is a similar dance like mem_cgroup_oom_control_write. > >>>>> > >>>> > >>>> I don't see why we have to. > >>>> > >>>> I believe in a A/B/C hierarchy, C should be perfectly able to set a > >>>> different limit than its parents. Note that this is not a boolean. > >>> > >>> Ohh, I wasn't clear enough. I am not against setting the _limit_ I just > >>> meant that the kmem_accounted should be consistent within the hierarchy. > >>> > >> > >> If a parent of yours is accounted, you get accounted as well. This is > >> not the state in this patch, but gets added later. Isn't this enough ? > > > > But if the parent is not accounted, you can set the children to be > > accounted, right? Or maybe this is changed later in the series? I didn't > > get to the end yet. > > > > Yes, you can. Do you see any problem with that? Well, if a child contributes with the kmem charges upwards the hierachy then a parent can have kmem.usage > 0 with disabled accounting. I am not saying this is a no-go but it definitely is confusing and I do not see any good reason for it. I've considered it as an overlook rather than a deliberate design decision. -- Michal Hocko SUSE Labs