From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752725Ab1IZWsF (ORCPT ); Mon, 26 Sep 2011 18:48:05 -0400 Received: from mx2.parallels.com ([64.131.90.16]:34361 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752039Ab1IZWsD (ORCPT ); Mon, 26 Sep 2011 18:48:03 -0400 Message-ID: <4E8100FC.10906@parallels.com> Date: Mon, 26 Sep 2011 19:47:24 -0300 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0.2) Gecko/20110906 Thunderbird/6.0.2 MIME-Version: 1.0 To: KAMEZAWA Hiroyuki CC: Balbir Singh , Greg Thelen , , , , , , , , Subject: Re: [PATCH v3 2/7] socket: initial cgroup code. References: <1316393805-3005-1-git-send-email-glommer@parallels.com> <1316393805-3005-3-git-send-email-glommer@parallels.com> <4E7A342B.5040608@parallels.com> <4E7DECF0.9050804@parallels.com> <20110926195213.12da87b4.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20110926195213.12da87b4.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [201.82.135.174] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/26/2011 07:52 AM, KAMEZAWA Hiroyuki wrote: > On Sat, 24 Sep 2011 11:45:04 -0300 > Glauber Costa wrote: > >> On 09/22/2011 12:09 PM, Balbir Singh wrote: >>> On Thu, Sep 22, 2011 at 11:30 AM, Greg Thelen wrote: >>>> On Wed, Sep 21, 2011 at 11:59 AM, Glauber Costa wrote: >>>>> Right now I am working under the assumption that tasks are long lived inside >>>>> the cgroup. Migration potentially introduces some nasty locking problems in >>>>> the mem_schedule path. >>>>> >>>>> Also, unless I am missing something, the memcg already has the policy of >>>>> not carrying charges around, probably because of this very same complexity. >>>>> >>>>> True that at least it won't EBUSY you... But I think this is at least a way >>>>> to guarantee that the cgroup under our nose won't disappear in the middle of >>>>> our allocations. >>>> >>>> Here's the memcg user page behavior using the same pattern: >>>> >>>> 1. user page P is allocate by task T in memcg M1 >>>> 2. T is moved to memcg M2. The P charge is left behind still charged >>>> to M1 if memory.move_charge_at_immigrate=0; or the charge is moved to >>>> M2 if memory.move_charge_at_immigrate=1. >>>> 3. rmdir M1 will try to reclaim P (if P was left in M1). If unable to >>>> reclaim, then P is recharged to parent(M1). >>>> >>> >>> We also have some magic in page_referenced() to remove pages >>> referenced from different containers. What we do is try not to >>> penalize a cgroup if another cgroup is referencing this page and the >>> page under consideration is being reclaimed from the cgroup that >>> touched it. >>> >>> Balbir Singh >> Do you guys see it as a showstopper for this series to be merged, or can >> we just TODO it ? >> > > In my experience, 'I can't rmdir cgroup.' is always an important/difficult > problem. The users cannot know where the accouting is leaking other than > kmem.usage_in_bytes or memory.usage_in_bytes. and can't fix the issue. > > please add EXPERIMENTAL to Kconfig until this is fixed. I am working on something here that may allow it. But I think it is independent of the rest, and I can repost the series fixing the problems raised here without it, + EXPERIMENTAL. Btw, using EXPERIMENTAL here is a very good idea. I think that we should turn EXPERIMENTAL on even if I fix for that exists, for a least a couple of months until we see how this thing really evolves. What do you think? >> I can push a proposal for it, but it would be done in a separate patch >> anyway. Also, we may be in better conditions to fix this when the slab >> part is merged - since it will likely have the same problems... >> > > Yes. considering sockets which can be shared between tasks(cgroups) > you'll finally need > - owner task of socket > - account moving callback > > Or disallow task moving once accounted. I personally think disallowing task movement once accounted is reasonable. At least for starters. I think I can add at least that to the next proposal. Famous last words is, it should not be that hard...