From: Quentin Perret <quentin.perret@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Saravana Kannan <skannan@codeaurora.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ingo Molnar <mingo@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Chris Redpath <chris.redpath@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Thara Gopinath <thara.gopinath@linaro.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Todd Kjos <tkjos@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
Steve Muckle <smuckle@google.com>,
adharmap@quicinc.com, skannan@quicinc.com,
Pavan Kondeti <pkondeti@codeaurora.org>,
Juri Lelli <juri.lelli@redhat.com>,
Eduardo Valentin <edubezval@gmail.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
currojerez@riseup.net, Javi Merino <javi.merino@kernel.org>,
linux-pm-owner@vger.kernel.org
Subject: Re: [PATCH v5 10/14] sched/cpufreq: Refactor the utilization aggregation method
Date: Thu, 2 Aug 2018 16:39:19 +0100 [thread overview]
Message-ID: <20180802153917.cpvls5hxkvevjh6s@queper01-lin> (raw)
In-Reply-To: <20180802130440.GW2476@hirez.programming.kicks-ass.net>
On Thursday 02 Aug 2018 at 15:04:40 (+0200), Peter Zijlstra wrote:
> On Wed, Aug 01, 2018 at 10:23:27AM +0100, Quentin Perret wrote:
> > On Wednesday 01 Aug 2018 at 10:35:32 (+0200), Rafael J. Wysocki wrote:
> > > On Wed, Aug 1, 2018 at 10:23 AM, Quentin Perret <quentin.perret@arm.com> wrote:
> > > > On Wednesday 01 Aug 2018 at 09:32:49 (+0200), Rafael J. Wysocki wrote:
> > > >> On Tue, Jul 31, 2018 at 9:31 PM, <skannan@codeaurora.org> wrote:
> > > >> >> On Monday 30 Jul 2018 at 12:35:27 (-0700), skannan@codeaurora.org wrote:
> > > >> >>> If it's going to be a different aggregation from what's done for
> > > >> >>> frequency
> > > >> >>> guidance, I don't see the point of having this inside schedutil. Why not
> > > >> >>> keep it inside the scheduler files?
> > > >> >>
> > > >> >> This code basically results from a discussion we had with Peter on v4.
> > > >> >> Keeping everything centralized can make sense from a maintenance
> > > >> >> perspective, I think. That makes it easy to see the impact of any change
> > > >> >> to utilization signals for both EAS and schedutil.
> > > >> >
> > > >> > In that case, I'd argue it makes more sense to keep the code centralized in
> > > >> > the scheduler. The scheduler can let schedutil know about the utilization
> > > >> > after it aggregates them. There's no need for a cpufreq governor to know
> > > >> > that there are scheduling classes or how many there are. And the scheduler
> > > >> > can then choose to aggregate one way for task packing and another way for
> > > >> > frequency guidance.
> > > >>
> > > >> Also the aggregate utilization may be used by cpuidle governors in
> > > >> principle to decide how deep they can go with idle state selection.
> > > >
> > > > The only issue I see with this right now is that some of the things done
> > > > in this function are policy decisions which really belong to the governor,
> > > > I think.
> > >
> > > Well, the scheduler makes policy decisions too, in quite a few places. :-)
> >
> > That is true ... ;-) But not so much about frequency selection yet I guess
>
> Well, sugov is part of the scheduler :-) It being so allows for the
> co-ordinated decision making required for EAS.
>
> > > The really important consideration here is whether or not there may be
> > > multiple governors making different policy decisions in that respect.
> > > If not, then where exactly the single policy decision is made doesn't
> > > particularly matter IMO.
> >
> > I think some users of the aggregated utilization signal do want to make
> > slightly different decisions (I'm thinking about the RT-go-to-max thing
> > again which makes perfect sense in sugov, but could possibly hurt EAS).
> >
> > So the "hard" part of this work is to figure out what really is a
> > governor-specific policy decision, and what is common between all users.
> > I put "hard" between quotes because I only see the case of RT as truly
> > sugov-specific for now.
> >
> > If we also want a special case for DL, Peter's enum should work OK, and
> > enable to add more special cases for new users (cpuidle ?) if needed.
> > But maybe that is something for later ?
>
> Right, I don't mind moving the function. What I do oppose is having two
> very similar functions in different translation units -- because then
> they _will_ diverge and result in 'funny' things.
Sounds good :-) Would kernel/sched/pelt.c be the right place then ? It's
cross-class and kinda pelt-related I guess
Thanks,
Quentin
next prev parent reply other threads:[~2018-08-02 15:39 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-24 12:25 [PATCH v5 00/14] Energy Aware Scheduling Quentin Perret
2018-07-24 12:25 ` [PATCH v5 01/14] sched: Relocate arch_scale_cpu_capacity Quentin Perret
2018-07-24 12:25 ` [PATCH v5 02/14] sched/cpufreq: Factor out utilization to frequency mapping Quentin Perret
2018-07-24 12:25 ` [PATCH v5 03/14] PM: Introduce an Energy Model management framework Quentin Perret
2018-08-09 21:52 ` Rafael J. Wysocki
2018-08-10 8:15 ` Quentin Perret
2018-08-10 8:41 ` Rafael J. Wysocki
2018-08-10 9:12 ` Quentin Perret
2018-08-10 11:13 ` Rafael J. Wysocki
2018-08-10 12:30 ` Quentin Perret
2018-08-12 9:49 ` Rafael J. Wysocki
2018-07-24 12:25 ` [PATCH v5 04/14] PM / EM: Expose the Energy Model in sysfs Quentin Perret
2018-07-24 12:25 ` [PATCH v5 05/14] sched/topology: Reference the Energy Model of CPUs when available Quentin Perret
2018-07-24 12:25 ` [PATCH v5 06/14] sched/topology: Lowest energy aware balancing sched_domain level pointer Quentin Perret
2018-07-26 16:00 ` Valentin Schneider
2018-07-26 17:01 ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 07/14] sched/topology: Introduce sched_energy_present static key Quentin Perret
2018-07-24 12:25 ` [PATCH v5 08/14] sched/fair: Clean-up update_sg_lb_stats parameters Quentin Perret
2018-07-24 12:25 ` [PATCH v5 09/14] sched: Add over-utilization/tipping point indicator Quentin Perret
2018-08-02 12:26 ` Peter Zijlstra
2018-08-02 13:03 ` Quentin Perret
2018-08-02 13:08 ` Peter Zijlstra
2018-08-02 13:18 ` Quentin Perret
2018-08-02 13:48 ` Vincent Guittot
2018-08-02 14:14 ` Quentin Perret
2018-08-02 15:14 ` Vincent Guittot
2018-08-02 15:30 ` Quentin Perret
2018-08-02 15:55 ` Vincent Guittot
2018-08-02 16:00 ` Quentin Perret
2018-08-02 16:07 ` Vincent Guittot
2018-08-02 16:10 ` Quentin Perret
2018-08-02 16:38 ` Vincent Guittot
2018-08-02 16:59 ` Quentin Perret
2018-08-03 7:48 ` Vincent Guittot
2018-08-03 8:18 ` Quentin Perret
2018-08-03 13:49 ` Vincent Guittot
2018-08-03 14:21 ` Vincent Guittot
2018-08-03 15:55 ` Quentin Perret
2018-08-06 8:40 ` Vincent Guittot
2018-08-06 9:43 ` Quentin Perret
2018-08-06 10:45 ` Vincent Guittot
2018-08-06 11:02 ` Quentin Perret
2018-08-06 10:08 ` Dietmar Eggemann
2018-08-06 10:33 ` Vincent Guittot
2018-08-06 12:29 ` Dietmar Eggemann
2018-08-06 12:37 ` Vincent Guittot
2018-08-06 13:20 ` Dietmar Eggemann
2018-08-09 9:30 ` Vincent Guittot
2018-08-09 9:38 ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 10/14] sched/cpufreq: Refactor the utilization aggregation method Quentin Perret
2018-07-30 19:35 ` skannan
2018-07-31 7:59 ` Quentin Perret
2018-07-31 19:31 ` skannan
2018-08-01 7:32 ` Rafael J. Wysocki
2018-08-01 8:23 ` Quentin Perret
2018-08-01 8:35 ` Rafael J. Wysocki
2018-08-01 9:23 ` Quentin Perret
2018-08-01 9:40 ` Rafael J. Wysocki
2018-08-02 13:04 ` Peter Zijlstra
2018-08-02 15:39 ` Quentin Perret [this message]
2018-08-03 13:04 ` Quentin Perret
2018-08-02 12:33 ` Peter Zijlstra
2018-08-02 12:45 ` Peter Zijlstra
2018-08-02 15:21 ` Quentin Perret
2018-08-02 17:36 ` Peter Zijlstra
2018-08-03 12:42 ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 11/14] sched/fair: Introduce an energy estimation helper function Quentin Perret
2018-07-24 12:25 ` [PATCH v5 12/14] sched/fair: Select an energy-efficient CPU on task wake-up Quentin Perret
2018-08-02 13:54 ` Peter Zijlstra
2018-08-02 16:21 ` Quentin Perret
2018-07-24 12:25 ` [PATCH v5 13/14] OPTIONAL: arch_topology: Start Energy Aware Scheduling Quentin Perret
2018-07-24 12:25 ` [PATCH v5 14/14] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret
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