From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx107.postini.com [74.125.245.107]) by kanga.kvack.org (Postfix) with SMTP id AAF316B007D for ; Tue, 19 Jun 2012 04:57:13 -0400 (EDT) Message-ID: <4FE03E4B.5020809@parallels.com> Date: Tue, 19 Jun 2012 12:54:35 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH v4 23/25] memcg: propagate kmem limiting information to children References: <1340015298-14133-1-git-send-email-glommer@parallels.com> <1340015298-14133-24-git-send-email-glommer@parallels.com> <4FDF20ED.4090401@jp.fujitsu.com> <4FDF227B.3080601@parallels.com> <4FDFC4D4.1030303@jp.fujitsu.com> <4FE039B9.3080809@parallels.com> In-Reply-To: <4FE039B9.3080809@parallels.com> Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Kamezawa Hiroyuki Cc: linux-mm@kvack.org, Pekka Enberg , Cristoph Lameter , David Rientjes , cgroups@vger.kernel.org, devel@openvz.org, linux-kernel@vger.kernel.org, Frederic Weisbecker , Suleiman Souhlal , Pekka Enberg , Michal Hocko , Johannes Weiner On 06/19/2012 12:35 PM, Glauber Costa wrote: > On 06/19/2012 04:16 AM, Kamezawa Hiroyuki wrote: >> (2012/06/18 21:43), Glauber Costa wrote: >>> On 06/18/2012 04:37 PM, Kamezawa Hiroyuki wrote: >>>> (2012/06/18 19:28), Glauber Costa wrote: >>>>> The current memcg slab cache management fails to present satisfatory hierarchical >>>>> behavior in the following scenario: >>>>> >>>>> -> /cgroups/memory/A/B/C >>>>> >>>>> * kmem limit set at A >>>>> * A and B empty taskwise >>>>> * bash in C does find / >>>>> >>>>> Because kmem_accounted is a boolean that was not set for C, no accounting >>>>> would be done. This is, however, not what we expect. >>>>> >>>> >>>> Hmm....do we need this new routines even while we have mem_cgroup_iter() ? >>>> >>>> Doesn't this work ? >>>> >>>> struct mem_cgroup { >>>> ..... >>>> bool kmem_accounted_this; >>>> atomic_t kmem_accounted; >>>> .... >>>> } >>>> >>>> at set limit >>>> >>>> ....set_limit(memcg) { >>>> >>>> if (newly accounted) { >>>> mem_cgroup_iter() { >>>> atomic_inc(&iter->kmem_accounted) >>>> } >>>> } else { >>>> mem_cgroup_iter() { >>>> atomic_dec(&iter->kmem_accounted); >>>> } >>>> } >>>> >>>> >>>> hm ? Then, you can see kmem is accounted or not by atomic_read(&memcg->kmem_accounted); >>>> >>> >>> Accounted by itself / parent is still useful, and I see no reason to use >>> an atomic + bool if we can use a pair of bits. >>> >>> As for the routine, I guess mem_cgroup_iter will work... It does a lot >>> more than I need, but for the sake of using what's already in there, I >>> can switch to it with no problems. >>> >> >> Hmm. please start from reusing existing routines. >> If it's not enough, some enhancement for generic cgroup will be welcomed >> rather than completely new one only for memcg. >> > > And now that I am trying to adapt the code to the new function, I > remember clearly why I done this way. Sorry for my failed memory. > > That has to do with the order of the walk. I need to enforce hierarchy, > which means whenever a cgroup has !use_hierarchy, I need to cut out that > branch, but continue scanning the tree for other branches. > > That is a lot easier to do with depth-search tree walks like the one > proposed in this patch. for_each_mem_cgroup() seems to walk the tree in > css-creation order. Which means we need to keep track of parents that > has hierarchy disabled at all times ( can be many ), and always test for > ancestorship - which is expensive, but I don't particularly care. > > But I'll give another shot with this one. > Humm, silly me. I was believing the hierarchical settings to be more flexible than they really are. I thought that it could be possible for a children of a parent with use_hierarchy = 1 to have use_hierarchy = 0. It seems not to be the case. This makes my life a lot easier. -- 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