From: Peter Zijlstra <peterz@infradead.org>
To: Quentin Perret <quentin.perret@arm.com>
Cc: rjw@rjwysocki.net, linux-kernel@vger.kernel.org,
linux-pm@vger.kernel.org, gregkh@linuxfoundation.org,
mingo@redhat.com, dietmar.eggemann@arm.com,
morten.rasmussen@arm.com, chris.redpath@arm.com,
patrick.bellasi@arm.com, valentin.schneider@arm.com,
vincent.guittot@linaro.org, thara.gopinath@linaro.org,
viresh.kumar@linaro.org, tkjos@google.com,
joel@joelfernandes.org, smuckle@google.com,
adharmap@codeaurora.org, skannan@codeaurora.org,
pkondeti@codeaurora.org, juri.lelli@redhat.com,
edubezval@gmail.com, srinivas.pandruvada@linux.intel.com,
currojerez@riseup.net, javi.merino@kernel.org
Subject: Re: [PATCH v7 03/14] PM: Introduce an Energy Model management framework
Date: Tue, 2 Oct 2018 14:25:35 +0200 [thread overview]
Message-ID: <20181002122535.GY3439@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180912091309.7551-4-quentin.perret@arm.com>
On Wed, Sep 12, 2018 at 10:12:58AM +0100, Quentin Perret wrote:
> +/**
> + * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf. domain
> + * @pd : performance domain for which energy has to be estimated
> + * @max_util : highest utilization among CPUs of the domain
> + * @sum_util : sum of the utilization of all CPUs in the domain
> + *
> + * Return: the sum of the energy consumed by the CPUs of the domain assuming
> + * a capacity state satisfying the max utilization of the domain.
> + */
> +static inline unsigned long em_pd_energy(struct em_perf_domain *pd,
> + unsigned long max_util, unsigned long sum_util)
> +{
> + unsigned long freq, scale_cpu;
> + struct em_cap_state *cs;
> + int i, cpu;
> +
> + /*
> + * In order to predict the capacity state, map the utilization of the
> + * most utilized CPU of the performance domain to a requested frequency,
> + * like schedutil.
> + */
> + cpu = cpumask_first(to_cpumask(pd->cpus));
> + scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
> + cs = &pd->table[pd->nr_cap_states - 1];
> + freq = map_util_freq(max_util, cs->frequency, scale_cpu);
> +
> + /*
> + * Find the lowest capacity state of the Energy Model above the
> + * requested frequency.
> + */
> + for (i = 0; i < pd->nr_cap_states; i++) {
> + cs = &pd->table[i];
> + if (cs->frequency >= freq)
> + break;
> + }
> +
> + /*
> + * The capacity of a CPU in the domain at that capacity state (cs)
> + * can be computed as:
> + *
> + * cs->freq * scale_cpu
> + * cs->cap = -------------------- (1)
> + * cpu_max_freq
> + *
> + * So, the energy consumed by this CPU at that capacity state is:
> + *
> + * cs->power * cpu_util
> + * cpu_nrg = -------------------- (2)
> + * cs->cap
> + *
> + * since 'cpu_util / cs->cap' represents its percentage of busy time.
> + *
> + * NOTE: Although the result of this computation actually is in
> + * units of power, it can be manipulated as an energy value
> + * over a scheduling period, since it is assumed to be
> + * constant during that interval.
> + *
> + * By injecting (1) in (2), 'cpu_nrg' can be re-expressed as a product
> + * of two terms:
> + *
> + * cs->power * cpu_max_freq cpu_util
> + * cpu_nrg = ------------------------ * --------- (3)
> + * cs->freq scale_cpu
> + *
> + * The first term is static, and is stored in the em_cap_state struct
> + * as 'cs->cost'.
> + *
> + * Since all CPUs of the domain have the same micro-architecture, they
> + * share the same 'cs->cost', and the same CPU capacity. Hence, the
> + * total energy of the domain (which is the simple sum of the energy of
> + * all of its CPUs) can be factorized as:
> + *
> + * cs->cost * \Sum cpu_util
> + * pd_nrg = ------------------------ (4)
> + * scale_cpu
> + */
> + return cs->cost * sum_util / scale_cpu;
> +}
Should we explicitly mention that this ignores idle costs?
next prev parent reply other threads:[~2018-10-02 12:25 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-12 9:12 [PATCH v7 00/14] Energy Aware Scheduling Quentin Perret
2018-09-12 9:12 ` [PATCH v7 01/14] sched: Relocate arch_scale_cpu_capacity Quentin Perret
2018-09-12 9:12 ` [PATCH v7 02/14] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling Quentin Perret
2018-09-12 14:56 ` Vincent Guittot
2018-09-18 21:33 ` Rafael J. Wysocki
2018-09-27 12:17 ` Quentin Perret
2018-09-28 8:23 ` Rafael J. Wysocki
2018-09-28 8:35 ` Quentin Perret
2018-09-28 8:35 ` Rafael J. Wysocki
2018-09-12 9:12 ` [PATCH v7 03/14] PM: Introduce an Energy Model management framework Quentin Perret
2018-10-02 12:25 ` Peter Zijlstra [this message]
2018-10-02 12:54 ` Quentin Perret
2018-10-02 13:50 ` Peter Zijlstra
2018-10-02 12:30 ` Peter Zijlstra
2018-10-02 12:51 ` Quentin Perret
2018-10-02 13:48 ` Peter Zijlstra
2018-10-02 14:05 ` Quentin Perret
2018-10-02 14:29 ` Peter Zijlstra
2018-10-02 14:40 ` Quentin Perret
2018-10-02 19:12 ` Andrea Parri
2018-10-03 7:48 ` Quentin Perret
2018-09-12 9:12 ` [PATCH v7 04/14] PM / EM: Expose the Energy Model in sysfs Quentin Perret
2018-09-12 9:13 ` [PATCH v7 05/14] sched: Introduce a sched_feat for Energy Aware Scheduling Quentin Perret
2018-10-02 12:34 ` Peter Zijlstra
2018-10-02 13:08 ` Quentin Perret
2018-10-03 16:24 ` Peter Zijlstra
2018-10-04 9:57 ` Quentin Perret
2018-09-12 9:13 ` [PATCH v7 06/14] sched/topology: Reference the Energy Model of CPUs when available Quentin Perret
2018-10-02 12:36 ` Peter Zijlstra
2018-10-02 13:16 ` Quentin Perret
2018-09-12 9:13 ` [PATCH v7 07/14] sched/topology: Lowest CPU asymmetry sched_domain level pointer Quentin Perret
2018-09-12 9:13 ` [PATCH v7 08/14] sched/topology: Disable EAS on inappropriate platforms Quentin Perret
2018-10-03 16:27 ` Peter Zijlstra
2018-10-04 9:10 ` Quentin Perret
2018-10-04 9:38 ` Peter Zijlstra
2018-10-04 9:45 ` Quentin Perret
2018-09-12 9:13 ` [PATCH v7 09/14] sched/fair: Clean-up update_sg_lb_stats parameters Quentin Perret
2018-09-12 9:13 ` [PATCH v7 10/14] sched: Add over-utilization/tipping point indicator Quentin Perret
2018-09-12 9:13 ` [PATCH v7 11/14] sched/fair: Introduce an energy estimation helper function Quentin Perret
2018-10-04 8:34 ` Peter Zijlstra
2018-10-04 9:02 ` Quentin Perret
2018-09-12 9:13 ` [PATCH v7 12/14] sched/fair: Select an energy-efficient CPU on task wake-up Quentin Perret
2018-10-04 9:44 ` Peter Zijlstra
2018-10-04 10:27 ` Quentin Perret
2018-10-04 10:41 ` Peter Zijlstra
2018-10-04 10:55 ` Quentin Perret
2018-10-04 12:18 ` Peter Zijlstra
2018-09-12 9:13 ` [PATCH v7 13/14] sched/topology: Make Energy Aware Scheduling depend on schedutil Quentin Perret
2018-10-04 10:50 ` Peter Zijlstra
2018-10-04 11:58 ` Quentin Perret
2018-09-12 9:13 ` [PATCH v7 14/14] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret
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