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SubjectRe: [PATCH 1/2] sched/fair: Take thermal pressure into account while estimating energy
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Hi Quentin,

On 6/2/21 4:00 PM, Quentin Perret wrote:
> Hi Lukasz,
>
> On Wednesday 02 Jun 2021 at 14:56:08 (+0100), Lukasz Luba wrote:
>> compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
>> {
>> struct cpumask *pd_mask = perf_domain_span(pd);
>> - unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
>> + unsigned long _cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
>> unsigned long max_util = 0, sum_util = 0;
>> + unsigned long cpu_cap = _cpu_cap;
>> int cpu;
>>
>> /*
>> @@ -6558,6 +6559,14 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
>> cpu_util_next(cpu, p, -1) + task_util_est(p);
>> }
>>
>> + /*
>> + * Take the thermal pressure from non-idle CPUs. They have
>> + * most up-to-date information. For idle CPUs thermal pressure
>> + * signal is not updated so often.
>> + */
>> + if (!idle_cpu(cpu))
>> + cpu_cap = _cpu_cap - thermal_load_avg(cpu_rq(cpu));
>
> This messes up the irq time scaling no? Maybe move the capping in this

You are talking about scale_irq_capacity() which shrinks the util by
some percentage of irq time. It might be different, by some fraction
(e.g. 8/9 vs 9/10) compared to SchedUtil view, which passes 'raw' arch
capacity. It then adds the irq part, but still to this slightly
different base util.

> function instead of relying on effective_cpu_util() to do it for you?

Agree, since it would be more 'aligned' with how SchedUtil calls
effective_cpu_util(). I will clamp the returned value.

Thanks for pointing this out.

Regards,
Lukasz

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