From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick Bellasi Subject: Re: [PATCH] sched/fair: schedutil: update only with all info available Date: Thu, 26 Apr 2018 12:15:33 +0100 Message-ID: <20180426111533.GX14248@e110439-lin> References: <20180406172835.20078-1-patrick.bellasi@arm.com> <20180410110412.GG14248@e110439-lin> <20180411151450.GK4043@hirez.programming.kicks-ass.net> <20180411153710.GN4082@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180411153710.GN4082@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org To: Peter Zijlstra Cc: Vincent Guittot , linux-kernel , "open list:THERMAL" , Ingo Molnar , "Rafael J . Wysocki" , Viresh Kumar , Juri Lelli , Joel Fernandes , Steve Muckle , Dietmar Eggemann , Morten Rasmussen List-Id: linux-pm@vger.kernel.org On 11-Apr 17:37, Peter Zijlstra wrote: > On Wed, Apr 11, 2018 at 05:29:01PM +0200, Vincent Guittot wrote: > > On 11 April 2018 at 17:14, Peter Zijlstra wrote: > > > On Tue, Apr 10, 2018 at 12:04:12PM +0100, Patrick Bellasi wrote: > > >> On 09-Apr 10:51, Vincent Guittot wrote: > > > > > >> > Peter, > > >> > what was your goal with adding the condition "if > > >> > (rq->cfs.h_nr_running)" for the aggragation of CFS utilization > > >> > > >> The original intent was to get rid of sched class flags, used to track > > >> which class has tasks runnable from within schedutil. The reason was > > >> to solve some misalignment between scheduler class status and > > >> schedutil status. > > >> > > >> The solution, initially suggested by Viresh, and finally proposed by > > >> Peter was to exploit RQ knowledges directly from within schedutil. > > >> > > >> The problem is that now schedutil updated depends on two information: > > >> utilization changes and number of RT and CFS runnable tasks. > > >> > > >> Thus, using cfs_rq::h_nr_running is not the problem... it's actually > > >> part of a much more clean solution of the code we used to have. > > >> > > >> The problem, IMO is that we now depend on other information which > > >> needs to be in sync before calling schedutil... and the patch I > > >> proposed is meant to make it less likely that all the information > > >> required are not aligned (also in the future). > > > > > > Specifically, the h_nr_running test was get rid of > > > > > > if (delta_ns > TICK_NSEC) { > > > j_sg_cpu->iowait_boost = 0; > > > j_sg_cpu->iowait_boost_pending = false; > > > - j_sg_cpu->util_cfs = 0; > > > > > > ^^^^^^^^^^^^^^^^^^^^^^^ that.. > > > > > > - if (j_sg_cpu->util_dl == 0) > > > - continue; > > > } > > > > > > > > > because that felt rather arbitrary. > > > > yes I agree. > > > > With the patch that updates blocked idle load, we should not have the > > problem of blocked utilization anymore and get rid of the code above > > and h_nr_running test > > Yes, these patches predate those, but indeed, now that we age the > blocked load consistently it should no longer be required. After this discussion, I think there is a general consensus about always add sg_cpu->util_cfs in cpufreq_schedutil.c::sugov_aggregate_util. Is that right? For the rest, what this patch proposes is a code reorganization which is not required anymore to fix this specific issue but, it's still required to fix the other issue reported by Vincent: i.e. util_est is not updated before schedutil. Thus, I would propose to still keep this refactoring but in the context of a different patch to specifically fixes the util_est case. If there are not major complains, I'll post a new series in the next few days. -- #include Patrick Bellasi