From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751716AbcBKMAF (ORCPT ); Thu, 11 Feb 2016 07:00:05 -0500 Received: from casper.infradead.org ([85.118.1.10]:60122 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751118AbcBKMAC (ORCPT ); Thu, 11 Feb 2016 07:00:02 -0500 Date: Thu, 11 Feb 2016 12:59:59 +0100 From: Peter Zijlstra To: Steve Muckle Cc: "Rafael J. Wysocki" , "Rafael J. Wysocki" , Linux PM list , Linux Kernel Mailing List , Srinivas Pandruvada , Viresh Kumar , Juri Lelli , Thomas Gleixner Subject: Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks Message-ID: <20160211115959.GI6357@twins.programming.kicks-ass.net> References: <3071836.JbNxX8hU6x@vostro.rjw.lan> <56B93548.9090006@linaro.org> <5387313.xAhVpzgZCg@vostro.rjw.lan> <56BA8C29.4090905@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56BA8C29.4090905@linaro.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 09, 2016 at 05:02:33PM -0800, Steve Muckle wrote: > > Index: linux-pm/kernel/sched/deadline.c > > =================================================================== > > --- linux-pm.orig/kernel/sched/deadline.c > > +++ linux-pm/kernel/sched/deadline.c > > @@ -1197,6 +1197,9 @@ static void task_tick_dl(struct rq *rq, > > { > > update_curr_dl(rq); > > > > + /* Kick cpufreq to prevent it from stalling. */ > > + cpufreq_kick(); > > + > > /* > > * Even when we have runtime, update_curr_dl() might have resulted in us > > * not being the leftmost task anymore. In that case NEED_RESCHED will > > I think additional hooks such as enqueue/dequeue would be needed in > RT/DL. The task tick callbacks will only run if a task in that class is > executing at the time of the tick. There could be intermittent RT/DL > task activity in a frequency domain (the only task activity there, no > CFS tasks) that doesn't happen to overlap the tick. Worst case the task > activity could be periodic in such a way that it never overlaps the tick > and the update is never made. No, for RT (RR/FIFO) we do not have enough information to do anything useful. Basically RR/FIFO should result in running 100% whenever we schedule such a task. That means RR/FIFO want a hook in pick_next_task_rt() to bump the freq to 100% and leave it there until something else gets to run. For DL it basically wants to set a minimum freq based on reserved utilization, so that is __setparam_dl() or somewhere around there. And we should either use CPPC hints for min freq or manually ensure that the CFS callback will not select something less than this.