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From: Paul Menage <menage@google.com>
To: balbir@linux.vnet.ibm.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>
Subject: Re: [mm] [PATCH 4/4] Memory cgroup hierarchy feature selector
Date: Mon, 3 Nov 2008 22:37:31 -0800	[thread overview]
Message-ID: <6599ad830811032237q14c065efx4316fee8f8daa515@mail.gmail.com> (raw)
In-Reply-To: <490DCCC9.5000508@linux.vnet.ibm.com>

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?

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.
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.

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

Paul

  reply	other threads:[~2008-11-04  6:37 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 [this message]
2008-11-06  7:00             ` Balbir Singh
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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