linux-kernel - Re: [PATCH] cgroup: remove extra calls to find_existing_css

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Message-ID: <20120129203749.GE17211@htj.dyndns.org>
Date:	Sun, 29 Jan 2012 12:37:49 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	Li Zefan <lizf@...fujitsu.com>, linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <paul@...lmenage.org>
Subject: Re: [PATCH] cgroup: remove extra calls to find_existing_css_set

Hello, Manddep.

On Tue, Jan 24, 2012 at 10:26:31AM -0800, Mandeep Singh Baines wrote:
> In cgroup_attach_proc, we indirectly call find_existing_css_set 3
> times. It is an expensive call so we want to call it a minimum
> of times. This patch only calls it once and stores the result so
> that it can be used later on when we call cgroup_task_migrate.
> 
> This required modifying cgroup_task_migrate to take the new css_set
> (which we obtained from find_css_set) as a parameter. The nice side
> effect of this is that cgroup_task_migrate is now identical for
> cgroup_attach_task and cgroup_attach_proc. It also now returns a
> void since it can never fail.
> 
> Changes in V5:
> * https://lkml.org/lkml/2012/1/20/344 (Tejun Heo)
>   * Remove css_set_refs
             ^^^^^^^^^^^^
>  static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
>  {
> -	int retval, i, group_size;
> +	int retval, i, group_size, css_set_refs = 0;
				   ^^^^^^^^^^^^
Wrong patch?

Thanks.

-- 
tejun
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