Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932488AbaKMKaR (ORCPT ); Thu, 13 Nov 2014 05:30:17 -0500 Received: from mail-pd0-f177.google.com ([209.85.192.177]:55470 "EHLO mail-pd0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932336AbaKMKaO (ORCPT ); Thu, 13 Nov 2014 05:30:14 -0500 Message-ID: <5464882D.40504@gmail.com> Date: Thu, 13 Nov 2014 18:30:05 +0800 From: Wanpeng Li User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Juri Lelli , Wanpeng Li , Ingo Molnar , Peter Zijlstra CC: Kirill Tkhai , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 2/2] sched/deadline: fix start high-res preemption tick for a non-running task References: <1415670747-58726-1-git-send-email-wanpeng.li@linux.intel.com> <1415670747-58726-2-git-send-email-wanpeng.li@linux.intel.com> <54647BDC.6050804@arm.com> In-Reply-To: <54647BDC.6050804@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Juri, On 11/13/14, 5:37 PM, Juri Lelli wrote: > Hi, > > not sure I understand what the problem is here. > > On 11/11/14 01:52, Wanpeng Li wrote: >> Queued ticks are scheduled to match the budget, which means the budget >> is overall consumed and the dl task should be throttled. > ... enforce the budget? It means that when the budget is consumed the > task has to be throttled... Agreed. > >> Dl task will >> be replenished immediately if fail to start a dl timer. >> >> However, the curr maybe not the left most dl task in the rb tree any >> more after this immediately replenished and reschedule is needed. >> Start high-res preemption tick for this upcoming rescheduled dl task >> is not correct. >> > So, the task that is going to preempt curr is picked by > pick_next_task_dl(), that correctly starts the hrtick for this new task. > > Maybe you can add more information about what you are seeing? A callpath > maybe? The parameter of task_tick_dl() queued == 1 means that hrtick is fired. hrtick() => task_tick_dl( , ,1), so p->dl.runtime should be <= 0 if queued == 1. What I see is queued == 1 && p->dl.runtime > 0 && p is not the left most task and hrtick is start for this task. Regards, Wanpeng Li > > Thanks, > > - Juri > >> This patch fix it by not starting high-res preemption tick for a >> non-running dl task. >> >> Signed-off-by: Wanpeng Li >> --- >> kernel/sched/deadline.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c >> index 56674f6..2a6a5bb 100644 >> --- a/kernel/sched/deadline.c >> +++ b/kernel/sched/deadline.c >> @@ -1090,7 +1090,8 @@ static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued) >> { >> update_curr_dl(rq); >> >> - if (hrtick_enabled(rq) && queued && p->dl.runtime > 0) >> + if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 && >> + is_leftmost(p, &rq->dl)) >> start_hrtick_dl(rq, p); >> } >> >> > -- > 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/ -- 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/