From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753913Ab3FFX4x (ORCPT ); Thu, 6 Jun 2013 19:56:53 -0400 Received: from mail-pa0-f51.google.com ([209.85.220.51]:40348 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752147Ab3FFX4v (ORCPT ); Thu, 6 Jun 2013 19:56:51 -0400 Date: Thu, 6 Jun 2013 16:56:47 -0700 From: Tejun Heo To: Glauber Costa Cc: Peter Zijlstra , Paul Turner , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Frederic Weisbecker , devel@openvz.org Subject: Re: [PATCH v7 08/11] sched: Push put_prev_task() into pick_next_task() Message-ID: <20130606235647.GR5045@htj.dyndns.org> References: <1369825402-31046-1-git-send-email-glommer@openvz.org> <1369825402-31046-9-git-send-email-glommer@openvz.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1369825402-31046-9-git-send-email-glommer@openvz.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 29, 2013 at 03:03:19PM +0400, Glauber Costa wrote: > From: Peter Zijlstra > > In order to avoid having to do put/set on a whole cgroup hierarchy > when we context switch, push the put into pick_next_task() so that > both operations are in the same function. Further changes then allow > us to possibly optimize away redundant work. I suppose this is to optimize out css_put/get() if the previous and next tasks are in the same group? css refcnt will soon (this week) be converted to percpu reference counter, so the optimization might not be as meaningful unless there are other things which are being optimized. Thanks. -- tejun