From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx202.postini.com [74.125.245.202]) by kanga.kvack.org (Postfix) with SMTP id 78CEA6B0072 for ; Tue, 19 Jun 2012 04:37:46 -0400 (EDT) Message-ID: <4FE039B9.3080809@parallels.com> Date: Tue, 19 Jun 2012 12:35:05 +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> In-Reply-To: <4FDFC4D4.1030303@jp.fujitsu.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 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. -- 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