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Date:   Wed, 2 Jun 2021 15:00:48 +0000
From:   Quentin Perret <qperret@google.com>
To:     Lukasz Luba <lukasz.luba@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        peterz@infradead.org, rjw@rjwysocki.net, viresh.kumar@linaro.org,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        vincent.donnefort@arm.com, mingo@redhat.com, juri.lelli@redhat.com,
        rostedt@goodmis.org, segall@google.com, mgorman@suse.de,
        bristot@redhat.com
Subject: Re: [PATCH 1/2] sched/fair: Take thermal pressure into account while
 estimating energy
Message-ID: <YLedIMNFlZ5eu2Oe@google.com>
References: <20210602135609.10867-1-lukasz.luba@arm.com>
 <20210602135609.10867-2-lukasz.luba@arm.com>
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In-Reply-To: <20210602135609.10867-2-lukasz.luba@arm.com>
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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
function instead of relying on effective_cpu_util() to do it for you?

>  		/*
>  		 * Busy time computation: utilization clamping is not
>  		 * required since the ratio (sum_util / cpu_capacity)
> -- 
> 2.17.1
>