From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754591AbdERCAR (ORCPT ); Wed, 17 May 2017 22:00:17 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:51607 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752721AbdERCAQ (ORCPT ); Wed, 17 May 2017 22:00:16 -0400 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, 18 May 2017 11:00:04 +0900 From: Byungchul Park To: peterz@infradead.org Cc: linux-kernel@vger.kernel.org, kernel-team@lge.com, rostedt@goodmis.org, juri.lelli@arm.com, bristot@redhat.com Subject: Re: [RESEND PATCH v3] sched/deadline: Remove unnecessary condition in push_dl_task() Message-ID: <20170518020004.GB28017@X58A-UD3R> References: <1494551159-22367-1-git-send-email-byungchul.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1494551159-22367-1-git-send-email-byungchul.park@lge.com> 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 Fri, May 12, 2017 at 10:05:59AM +0900, Byungchul Park wrote: > pick_next_pushable_dl_task(rq) 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. So if task == next_task, then task_cpu(next_task) must > be rq->cpu as well. Remove the redundant condition and make code simpler. > > By this patch, unnecessary one branch and two LOAD operations in 'if' > statement can be avoided. +cc rostedt@goodmis.org +cc juri.lelli@arm.com +cc bristot@redhat.com > > Signed-off-by: Byungchul Park > Reviewed-by: Steven Rostedt (VMware) > Reviewed-by: Juri Lelli > Reviewed-by: Daniel Bristot de Oliveira > --- > 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) { > /* > * The task is still there. We don't try > * again, some other cpu will pull it when ready. > -- > 1.9.1