From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752080AbdBOLhv (ORCPT ); Wed, 15 Feb 2017 06:37:51 -0500 Received: from merlin.infradead.org ([205.233.59.134]:58546 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752005AbdBOLht (ORCPT ); Wed, 15 Feb 2017 06:37:49 -0500 Date: Wed, 15 Feb 2017 12:37:36 +0100 From: Peter Zijlstra To: Juri Lelli Cc: Byungchul Park , mingo@kernel.org, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, kernel-team@lge.com, Steven Rostedt , Luca Abeni Subject: Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task() Message-ID: <20170215113736.GV6500@twins.programming.kicks-ass.net> References: <1487135511-15817-1-git-send-email-byungchul.park@lge.com> <20170215104749.GB1368@e106622-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170215104749.GB1368@e106622-lin> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 15, 2017 at 10:47:49AM +0000, Juri Lelli wrote: > [+Steve, Luca] > > Hi, > > On 15/02/17 14:11, Byungchul Park wrote: > > Once pick_next_pushable_dl_task(rq) return a task, it guarantees that > > the task's cpu is rq->cpu, so task_cpu(next_task) is always rq->cpu if > > task == next_task. Remove a redundant condition and make code simpler. > > > > Signed-off-by: Byungchul Park > > --- > > kernel/sched/deadline.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > index 27737f3..ad8d577 100644 > > --- a/kernel/sched/deadline.c > > +++ b/kernel/sched/deadline.c > > @@ -1483,7 +1483,7 @@ static int push_dl_task(struct rq *rq) > > * then possible that next_task has migrated. > > */ > > task = pick_next_pushable_dl_task(rq); > > - if (task_cpu(next_task) == rq->cpu && task == next_task) { > > + if (task == next_task) { > > Seems a sensible optimization to me. Actually, we are doing the same for > rt.c; Steve, Peter, do you think we should optimize that as well? > If correct (and I've not spend brain cycles on that) yes. We should keep this push-pull muck synced between rt and deadline as much as possible.