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Message-ID: <20190122121321.r6mv23ao57uut3t7@queper01-lin>
Date: Tue, 22 Jan 2019 12:13:22 +0000
From: Quentin Perret <quentin.perret@....com>
To: Patrick Bellasi <patrick.bellasi@....com>
Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Tejun Heo <tj@...nel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Paul Turner <pjt@...gle.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Morten Rasmussen <morten.rasmussen@....com>,
Juri Lelli <juri.lelli@...hat.com>,
Todd Kjos <tkjos@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
Steve Muckle <smuckle@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v6 11/16] sched/fair: Add uclamp support to
energy_compute()
On Tuesday 15 Jan 2019 at 10:15:08 (+0000), Patrick Bellasi wrote:
> The Energy Aware Scheduler (AES) estimates the energy impact of waking
s/AES/EAS :-)
[...]
> + for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
> + cfs_util = cpu_util_next(cpu, p, dst_cpu);
> +
> + /*
> + * Busy time computation: utilization clamping is not
> + * required since the ratio (sum_util / cpu_capacity)
> + * is already enough to scale the EM reported power
> + * consumption at the (eventually clamped) cpu_capacity.
> + */
Right.
> + sum_util += schedutil_cpu_util(cpu, cfs_util, cpu_cap,
> + ENERGY_UTIL, NULL);
> +
> + /*
> + * Performance domain frequency: utilization clamping
> + * must be considered since it affects the selection
> + * of the performance domain frequency.
> + */
So that actually affects the way we deal with RT I think. I assume the
idea is to say if you don't want to reflect the RT-go-to-max-freq thing
in EAS (which is what we do now) you should set the min cap for RT to 0.
Is that correct ?
I'm fine with this conceptually but maybe the specific case of RT should
be mentioned somewhere in the commit message or so ? I think it's
important to say that clearly since this patch changes the default
behaviour.
> + cpu_util = schedutil_cpu_util(cpu, cfs_util, cpu_cap,
> + FREQUENCY_UTIL,
> + cpu == dst_cpu ? p : NULL);
> + max_util = max(max_util, cpu_util);
> }
>
> energy += em_pd_energy(pd->em_pd, max_util, sum_util);
Thanks,
Quentin
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