From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752993AbdBPCSa (ORCPT ); Wed, 15 Feb 2017 21:18:30 -0500 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:40958 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752527AbdBPCS3 (ORCPT ); Wed, 15 Feb 2017 21:18:29 -0500 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Thu, 16 Feb 2017 11:17:58 +0900 From: Byungchul Park To: Juri Lelli Cc: Steven Rostedt , peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, kernel-team@lge.com, Luca Abeni Subject: Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task() Message-ID: <20170216021758.GS16086@X58A-UD3R> References: <1487135511-15817-1-git-send-email-byungchul.park@lge.com> <20170215104749.GB1368@e106622-lin> <20170215092507.106f7964@gandalf.local.home> <20170215144503.GG1368@e106622-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170215144503.GG1368@e106622-lin> 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, Feb 15, 2017 at 02:45:03PM +0000, Juri Lelli wrote: > On 15/02/17 09:25, Steven Rostedt wrote: > > On Wed, 15 Feb 2017 10:47:49 +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? > > > > > > > Are we doing the same for push_rt_task()? I don't see it, and I don't > > see it in tip/sched/core either. What I have is: > > > > if (task_cpu(next_task) == rq->cpu && task == next_task) { > > Sorry, bad wording on my side. I meant the are currently checking the > same conditions both for DL and for RT, and we should probably optimize > RT as well if we are going to take this patch. > > > > > But that said, I believe this patch is correct, and we should change > > rt.c as well. > > > > That's what I meant. :) > > > > > task = pick_next_pushable_dl_task(rq); > > > > Which has: > > > > BUG_ON(rq->cpu != task_cpu(task)) > > > > when it returns a task other than NULL. Which means that task_cpu(task) > > must be rq->cpu. Then if task == next_task, then task_cpu(next_task) > > must be rq->cpu as well. > > Right. > > > > > Reviewed-by: Steven Rostedt (VMware) > > > > You can also add mine > > Reviewed-by: Juri Lelli Juri and steven, thank you very much for reviewing it. I'm not sure and familiar with... Should I add your 'reviewed by' into my patches by myself? > > > Mind fixing rt.c if it hasn't been fixed already. > > > > -- Steve