Re: [PATCH V2 1/3] Calculate Thermal Pressure

From: Quentin Perret <quentin.perret@arm.com>
To: Thara Gopinath <thara.gopinath@linaro.org>
Cc: mingo@redhat.com, peterz@infradead.org, rui.zhang@intel.com,
	linux-kernel@vger.kernel.org, amit.kachhap@gmail.com,
	viresh.kumar@linaro.org, javi.merino@kernel.org,
	edubezval@gmail.com, daniel.lezcano@linaro.org,
	vincent.guittot@linaro.org, nicolas.dechesne@linaro.org,
	bjorn.andersson@linaro.org, dietmar.eggemann@arm.com
Subject: Re: [PATCH V2 1/3] Calculate Thermal Pressure
Date: Thu, 18 Apr 2019 11:14:20 +0100	[thread overview]
Message-ID: <20190418101418.5kiw5hkxoflbsvlj@queper01-lin> (raw)
In-Reply-To: <1555443521-579-2-git-send-email-thara.gopinath@linaro.org>

On Tuesday 16 Apr 2019 at 15:38:39 (-0400), Thara Gopinath wrote:
> +/**
> + * Function to update thermal pressure from cooling device
> + * or any framework responsible for capping cpu maximum
> + * capacity.
> + */
> +void sched_update_thermal_pressure(struct cpumask *cpus,
> +				   unsigned long cap_max_freq,
> +				   unsigned long max_freq)
> +{
> +	int cpu;
> +	unsigned long flags = 0;
> +	struct thermal_pressure *cpu_thermal;
> +
> +	for_each_cpu(cpu, cpus) {

Is it actually required to do this for each CPU ? You could calculate
the whole thing once for the first CPU, and apply the result to all CPUs
in the policy no ? All CPUs in a policy are capped and uncapped
synchronously.

> +		cpu_thermal = per_cpu(thermal_pressure_cpu, cpu);
> +		if (!cpu_thermal)
> +			return;
> +		spin_lock_irqsave(&cpu_thermal->lock, flags);
> +		thermal_pressure_update(cpu_thermal, cap_max_freq, max_freq, 1);
> +	}
> +}