Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936114AbXHIIjW (ORCPT ); Thu, 9 Aug 2007 04:39:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754665AbXHIIjO (ORCPT ); Thu, 9 Aug 2007 04:39:14 -0400 Received: from wa-out-1112.google.com ([209.85.146.182]:59489 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757569AbXHIIjN (ORCPT ); Thu, 9 Aug 2007 04:39:13 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=r1ck9IWkLAPLYJWqtyuvwHTbwLmVglsc0XiGsj15uiTM1mesZyS5Dxk+GZ5lJgjhvxDM3KDdXxvjdLXLinP6Zbl/6zQF8FCjSspeB5WLh/XqyKbNtTbR2vMwFQsRRoVCBbcCpPVZAIZyyybqXdIF8kdEH5nHJdDLEyxXk5BjXpA= Message-ID: Date: Thu, 9 Aug 2007 10:39:13 +0200 From: "Dmitry Adamushko" To: "Ingo Molnar" Subject: Re: Question: RT schedular : task_tick_rt(struct rq *rq, struct task_struct *p) : decreases overhead when rq->nr_running == 1 Cc: "Mitchell Erblich" , "Linux Kernel" In-Reply-To: <20070809083606.GA24130@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <000501c7d945$f30af1a0$6501a8c0@earthlink.net> <20070808123418.GA30248@elte.hu> <20070809082656.GA21973@elte.hu> <20070809083606.GA24130@elte.hu> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1971 Lines: 68 On 09/08/07, Ingo Molnar wrote: > > FYI, that's the patch i applied: Thanks. Added my SOB below. > > ---------------------------> > Subject: sched: optimize task_tick_rt() a bit > From: Dmitry Adamushko > > Mitchell Erblich suggested a change to not requeue SCHED_RR > tasks if there's only a single task on the runqueue, by > checking for rq->nr_running == 1. > > provide a more efficient implementation of that, to check that > particular RT priority-queue only. > > [ From: mingo@elte.hu ] > > Also first requeue the task then set need_resched - results > in slightly better machine-instruction ordering. Also clean > up the code a bit. > > Signed-off-by: Ingo Molnar Signed-off-by: Dmitry Adamushko > --- > kernel/sched_rt.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > Index: linux/kernel/sched_rt.c > =================================================================== > --- linux.orig/kernel/sched_rt.c > +++ linux/kernel/sched_rt.c > @@ -207,10 +207,15 @@ static void task_tick_rt(struct rq *rq, > return; > > p->time_slice = static_prio_timeslice(p->static_prio); > - set_tsk_need_resched(p); > > - /* put it at the end of the queue: */ > - requeue_task_rt(rq, p); > + /* > + * Requeue to the end of queue if we are not the only element > + * on the queue: > + */ > + if (p->run_list.prev != p->run_list.next) { > + requeue_task_rt(rq, p); > + set_tsk_need_resched(p); > + } > } > > static struct sched_class rt_sched_class __read_mostly = { > -- Best regards, Dmitry Adamushko - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/