From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753311AbaAQP0c (ORCPT ); Fri, 17 Jan 2014 10:26:32 -0500 Received: from mail-we0-f172.google.com ([74.125.82.172]:58741 "EHLO mail-we0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752615AbaAQP0Q (ORCPT ); Fri, 17 Jan 2014 10:26:16 -0500 Message-ID: <52D94B95.2060704@linaro.org> Date: Fri, 17 Jan 2014 16:26:13 +0100 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Peter Zijlstra CC: mingo@kernel.org, linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org, alex.shi@linaro.org Subject: Re: [PATCH 4/4] sched: Idle task shortcut optimization References: <1389949444-14821-1-git-send-email-daniel.lezcano@linaro.org> <1389949444-14821-4-git-send-email-daniel.lezcano@linaro.org> <20140117142644.GI11314@laptop.programming.kicks-ass.net> <52D94705.1000407@linaro.org> <20140117152310.GK11314@laptop.programming.kicks-ass.net> In-Reply-To: <20140117152310.GK11314@laptop.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/17/2014 04:23 PM, Peter Zijlstra wrote: > On Fri, Jan 17, 2014 at 04:06:45PM +0100, Daniel Lezcano wrote: >>> I suppose we could write something like: >>> >>> struct task_struct *pick_next_task(struct rq *rq, struct task_struct *prev) >>> { >>> const struct sched_class *class; >>> struct task_struct *p; >>> >>> again: >>> if (likely(rq->nr_running)) { >>> >>> if (likely(rq->nr_running == rq->cfs.h_nr_running)) >>> return fair_sched_class.pick_next_task(rq, prev); >>> >>> for_each_class(class) { >>> p = class->pick_next_task(rq, prev); >>> if (p) >>> return p; >>> } >>> } >>> >>> if (idle_balance(rq)) >>> goto again; >>> >>> rq->idle_stamp = rq_clock(rq); >>> >>> return idle_sched_class.pick_next_task(rq, prev); >>> } >>> >>> Which keeps idle_balance() before put_prev_task(), and by using >>> idle_sched_clas.pick_next_task() doesn't rape the idle class interface >>> like you did :-) >> >> But put_prev_task is called before pick_next_task, so idle_balance() is >> called after now, no ? > > No, put_prev_task() is called by the pick_next_task() that returns a > task. So in the idle case above, the idle_sched_class.pick_next_task() > will do the required put_prev_task(). Ah, ok. Let me try it. -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog