From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751272AbdEaKa3 (ORCPT ); Wed, 31 May 2017 06:30:29 -0400 Received: from merlin.infradead.org ([205.233.59.134]:36754 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750912AbdEaKa1 (ORCPT ); Wed, 31 May 2017 06:30:27 -0400 Date: Wed, 31 May 2017 12:30:17 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, juri.lelli@arm.com, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com Subject: Re: [RFC PATCH 1/2] sched/rt: add utilization tracking Message-ID: <20170531103017.3voouif2ixwbpbyn@hirez.programming.kicks-ass.net> References: <1495616452-7582-1-git-send-email-vincent.guittot@linaro.org> <1495616452-7582-2-git-send-email-vincent.guittot@linaro.org> <20170531094047.p3kkmj3xnhvunabu@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170531094047.p3kkmj3xnhvunabu@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 31, 2017 at 11:40:47AM +0200, Peter Zijlstra wrote: > On Wed, May 24, 2017 at 11:00:51AM +0200, Vincent Guittot wrote: > > schedutil governor relies on cfs_rq's util_avg to choose the OPP when cfs > > tasks are running. When the CPU is overloaded by cfs and rt tasks, cfs tasks > > are preempted by rt tasks and in this case util_avg reflects the remaining > > capacity that is used by cfs tasks but not what cfs tasks want to use. In such > > case, schedutil can select a lower OPP when cfs task runs whereas the CPU is > > overloaded. In order to have a more accurate view of the utilization of the > > CPU, we track the utilization that is used by RT tasks. > > DL tasks are not taken into account as they have their own utilization > > tracking mecanism. > > Well, the DL tracking is fairly pessimistic; it assumes all DL tasks > will consume their total budget, which will rarely, if ever, happen. > > So I suspect it might well be worth it to also track DL activity for the > purpose of compensating CFS. Again, it seems I have this CPPC/HWP crud firmly stuck in my brain. Because I was thinking: min_freq = dl_util avg_freq = dl_avg + rt_avg + cfs_util But given we don't actually have that split... meh. > In fact, I don't think you particularly care about RT here, as anything > !CFS that preempts it, including those interrupts you mentioned. Which > gets us back to what rt_avg is. > > > We don't use rt_avg which doesn't have the same dynamic as PELT and which > > can include IRQ time that are also accounted in cfs task utilization > > Well, if rt_avg includes IRQ time, then that IRQ time is not part of > the task clock.