linux-kernel - Re: [PATCH 1/9] Remove parent field in cpuacct cgroup

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Message-ID: <1316448186.1511.19.camel@twins>
Date:	Mon, 19 Sep 2011 18:03:05 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, xemul@...allels.com,
	paul@...lmenage.org, lizf@...fujitsu.com, daniel.lezcano@...e.fr,
	mingo@...e.hu, jbottomley@...allels.com
Subject: Re: [PATCH 1/9] Remove parent field in cpuacct cgroup

On Wed, 2011-09-14 at 17:04 -0300, Glauber Costa wrote:
> +       for (; ca; ca = parent_ca(ca)) {

It might be good to check that the loop condition and null condition in
the parent_ca() function get folded. Otherwise there's a double branch
in that loop.

Note that this function is one of the reasons I dislike cpuacct, it adds
a second cgroup hierarchy traversal to every context switch.

Cache-miss heaven all this.
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