linux-kernel - Re: [PATCH v8 11/16] sched/fair: uclamp: Add uclamp support to energy

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Date:   Thu, 9 May 2019 14:51:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
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>,
        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>,
        Quentin Perret <quentin.perret@....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 v8 11/16] sched/fair: uclamp: Add uclamp support to
 energy_compute()

On Tue, Apr 02, 2019 at 11:41:47AM +0100, Patrick Bellasi wrote:
> @@ -6484,11 +6494,29 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
>  		 * it will not appear in its pd list and will not be accounted
>  		 * by compute_energy().
>  		 */
> -		for_each_cpu_and(cpu, perf_domain_span(pd), cpu_online_mask) {
> -			util = cpu_util_next(cpu, p, dst_cpu);
> -			util = schedutil_energy_util(cpu, util);
> -			max_util = max(util, max_util);
> -			sum_util += util;
> +		for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
> +			util_cfs = 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.
> +			 */
> +			sum_util += schedutil_cpu_util(cpu, util_cfs, cpu_cap,
> +						       ENERGY_UTIL, NULL);
> +
> +			/*
> +			 * Performance domain frequency: utilization clamping
> +			 * must be considered since it affects the selection
> +			 * of the performance domain frequency.
> +			 * NOTE: in case RT tasks are running, by default the
> +			 * FREQUENCY_UTIL's utilization can be max OPP.
> +			 */
> +			tsk = cpu == dst_cpu ? p : NULL;
> +			cpu_util = schedutil_cpu_util(cpu, util_cfs, cpu_cap,
> +						      FREQUENCY_UTIL, tsk);
> +			max_util = max(max_util, cpu_util);
>  		}

That's a bit unfortunate; having to do both variants here, but I see
why. Nothing to be done about it I suppose.