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From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: linux-mm@kvack.org, YAMAMOTO Takashi <yamamoto@valinux.co.jp>,
	Paul Menage <menage@google.com>,
	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 2/4] Memory cgroup resource counters for hierarchy
Date: Sun, 02 Nov 2008 17:16:35 +0530	[thread overview]
Message-ID: <490D931B.8000200@linux.vnet.ibm.com> (raw)
In-Reply-To: <20081102145641.a15f5bb3.kamezawa.hiroyu@jp.fujitsu.com>

KAMEZAWA Hiroyuki wrote:
> On Sun, 02 Nov 2008 11:19:38 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
>> KAMEZAWA Hiroyuki wrote:
>>> On Sun, 02 Nov 2008 00:18:37 +0530
>>> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>>>
>>>> Add support for building hierarchies in resource counters. Cgroups allows us
>>>> to build a deep hierarchy, but we currently don't link the resource counters
>>>> belonging to the memory controller control groups, which are linked in
>>>> cgroup hiearchy. This patch provides the infrastructure for resource counters
>>>> that have the same hiearchy as their cgroup counter parts.
>>>>
>>>> These set of patches are based on the resource counter hiearchy patches posted
>>>> by Pavel Emelianov.
>>>>
>>>> NOTE: Building hiearchies is expensive, deeper hierarchies imply charging
>>>> the all the way up to the root. It is known that hiearchies are expensive,
>>>> so the user needs to be careful and aware of the trade-offs before creating
>>>> very deep ones.
>>>>
>>> ...isn't it better to add "root_lock" to res_counter rather than taking
>>> all levels of lock one by one ?
>>>
>>>  spin_lock(&res_counter->hierarchy_root->lock);
>>>  do all charge/uncharge to hierarchy
>>>  spin_unlock(&res_counter->hierarchy_root->lock);
>>>
>>> Hmm ?
>>>
>> Good thought process, but that affects and adds code complexity for the case
>> when hierarchy is enabled/disabled. It is also inefficient, since all charges
>> will now contend on root lock, in the current process, it is step by step, the
>> contention only occurs on common parts of the hierarchy (root being the best case).
>>
> 
> Above code's contention level is not different from "only root no children" case.
> Just inside-lock is heavier.

Yes, correct! I think the approach in the patches is better.

-- 
	Balbir

  reply	other threads:[~2008-11-02 11:47 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 [this message]
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
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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