linux-kernel - Re: [PATCH 5/7] cgroups: Ability to stop res charge propagation on bounded ancestor

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Message-Id: <20110712091131.e74d18f4.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 12 Jul 2011 09:11:31 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Aditya Kali <adityakali@...gle.com>
Subject: Re: [PATCH 5/7] cgroups: Ability to stop res charge propagation on
 bounded ancestor

On Mon, 11 Jul 2011 16:15:04 +0200
Frederic Weisbecker <fweisbec@...il.com> wrote:

> Moving a task from a cgroup to another may require to substract
> its resource charge from the old cgroup and add it to the new one.
> 
> For this to happen, the uncharge/charge propagation can just stop
> when we reach the common ancestor for the two cgroups. Further
> the performance reasons, we also want to avoid to temporarily
> overload the common ancestors with a non-accurate resource
> counter usage if we charge first the new cgroup and uncharge the
> old one thereafter. This is going to be a requirement for the coming
> max number of task subsystem.
> 
> To solve this, provide a pair of new API that can charge/uncharge
> a resource counter until we reach a given ancestor.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Paul Menage <menage@...gle.com>
> Cc: Li Zefan <lizf@...fujitsu.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Aditya Kali <adityakali@...gle.com>


Hmm, do you have the number to show the benefit of this new function ?
And....tasks is moving among cgroups so frequently as to show the benefit
of this function in your environment ??

Thanks,
-Kame

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