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From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	linux-mm@kvack.org, YAMAMOTO Takashi <yamamoto@valinux.co.jp>,
	lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org,
	Nick Piggin <nickpiggin@yahoo.com.au>,
	David Rientjes <rientjes@google.com>,
	Pavel Emelianov <xemul@openvz.org>,
	Dhaval Giani <dhaval@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dhaval Giani <dhaval@linux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@in.ibm.com>
Subject: Re: [mm] [PATCH 4/4] Memory cgroup hierarchy feature selector
Date: Thu, 06 Nov 2008 12:30:17 +0530	[thread overview]
Message-ID: <49129601.4040008@linux.vnet.ibm.com> (raw)
In-Reply-To: <6599ad830811032237q14c065efx4316fee8f8daa515@mail.gmail.com>

Paul Menage wrote:
> On Sun, Nov 2, 2008 at 7:52 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>> That should not be hard, but having it per-subtree sounds a little complex in
>> terms of exploiting from the end-user perspective and from symmetry perspective
>> (the CPU cgroup controller provides hierarchy control for the full hierarchy).
>>
> 
> The difference is that the CPU controller works in terms of shares,
> whereas memory works in terms of absolute memory size. So it pretty
> much has to limit the hierarchy to a single tree. Also, I didn't think
> that you could modify the shares for the root cgroup - what would that
> mean if so?
> 

The shares are proportional for the CPU controller. I am confused as to which
shares (CPU you are talking about?

> With this patch set as it is now, the root cgroup's lock becomes a
> global memory allocation/deallocation lock, which seems a bit painful.

Yes, true, but then that is the cost associated with using a hierarchy.

> Having a bunch of top-level cgroups each with their own independent
> memory limits, and allowing sub cgroups of them to be constrained by
> the parent's memory limit, seems more useful than a single hierarchy
> connected at the root.

That is certainly do-able, but can be confusing to users, given how other
controllers work. We can document that

> 
> In what realistic circumstances do you actually want to limit the root
> cgroup's memory usage?
> 

Good point, I would expect that people would mostly use the hierarchy with
soft-limits or shares. I am now beginning to like Kamezawa and your suggestion
of limiting usage to subtrees.


-- 
	Balbir

  reply	other threads:[~2008-11-06  7:29 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-01 18:48 [mm][PATCH 0/4] Memory cgroup hierarchy introduction Balbir Singh
2008-11-01 18:48 ` [mm] [PATCH 1/4] Memory cgroup hierarchy documentation Balbir Singh
2008-11-04  6:25   ` Paul Menage
2008-11-04  6:26     ` Paul Menage
2008-11-05 13:55       ` Balbir Singh
2008-11-01 18:48 ` [mm] [PATCH 2/4] Memory cgroup resource counters for hierarchy Balbir Singh
2008-11-02  5:42   ` KAMEZAWA Hiroyuki
2008-11-02  5:49     ` Balbir Singh
2008-11-02  5:56       ` KAMEZAWA Hiroyuki
2008-11-02 11:46         ` Balbir Singh
2008-11-01 18:48 ` [mm] [PATCH 3/4] Memory cgroup hierarchical reclaim Balbir Singh
2008-11-02  5:37   ` KAMEZAWA Hiroyuki
2008-11-02  5:44     ` Balbir Singh
2008-11-04  2:17       ` KAMEZAWA Hiroyuki
2008-11-05 13:34         ` Balbir Singh
2008-11-05 16:20           ` KAMEZAWA Hiroyuki
2008-11-06 14:00             ` Balbir Singh
2008-11-01 18:49 ` [mm] [PATCH 4/4] Memory cgroup hierarchy feature selector Balbir Singh
2008-11-02  5:38   ` KAMEZAWA Hiroyuki
2008-11-02  6:03     ` Balbir Singh
2008-11-02  6:24       ` KAMEZAWA Hiroyuki
2008-11-02 15:52         ` Balbir Singh
2008-11-04  6:37           ` Paul Menage
2008-11-06  7:00             ` Balbir Singh [this message]
2008-11-06  7:01               ` Balbir Singh
2008-11-06  6:56         ` Balbir Singh
2008-11-06  7:30           ` KAMEZAWA Hiroyuki
2008-11-04  0:15 ` [mm][PATCH 0/4] Memory cgroup hierarchy introduction KAMEZAWA Hiroyuki
2008-11-05 13:51   ` Balbir Singh
2008-11-05 16:33     ` KAMEZAWA Hiroyuki
2008-11-05 17:52       ` Balbir Singh
2008-11-06  0:22         ` KAMEZAWA Hiroyuki
2008-11-04  9:21 ` [patch 1/2] memcg: hierarchy, yet another one KAMEZAWA Hiroyuki
2008-11-04  9:25 ` KAMEZAWA Hiroyuki

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