From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756456Ab1ISQDe (ORCPT ); Mon, 19 Sep 2011 12:03:34 -0400 Received: from merlin.infradead.org ([205.233.59.134]:44135 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756032Ab1ISQDd convert rfc822-to-8bit (ORCPT ); Mon, 19 Sep 2011 12:03:33 -0400 Subject: Re: [PATCH 1/9] Remove parent field in cpuacct cgroup From: Peter Zijlstra To: Glauber Costa Cc: linux-kernel@vger.kernel.org, xemul@parallels.com, paul@paulmenage.org, lizf@cn.fujitsu.com, daniel.lezcano@free.fr, mingo@elte.hu, jbottomley@parallels.com Date: Mon, 19 Sep 2011 18:03:05 +0200 In-Reply-To: <1316030695-19826-2-git-send-email-glommer@parallels.com> References: <1316030695-19826-1-git-send-email-glommer@parallels.com> <1316030695-19826-2-git-send-email-glommer@parallels.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.3- Message-ID: <1316448186.1511.19.camel@twins> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.