linux-kernel - Re: [PATCH v3 1/3] thermal: cpufreq_cooling: Update also offline CPUs per-cpu thermal

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Date:   Mon, 14 Jun 2021 15:42:13 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        peterz@...radead.org, rjw@...ysocki.net,
        vincent.guittot@...aro.org, qperret@...gle.com,
        dietmar.eggemann@....com, vincent.donnefort@....com,
        Beata.Michalska@....com, mingo@...hat.com, juri.lelli@...hat.com,
        rostedt@...dmis.org, segall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, thara.gopinath@...aro.org,
        amit.kachhap@...il.com, amitk@...nel.org, rui.zhang@...el.com,
        daniel.lezcano@...aro.org
Subject: Re: [PATCH v3 1/3] thermal: cpufreq_cooling: Update also offline
 CPUs per-cpu thermal_pressure

On 10-06-21, 16:03, Lukasz Luba wrote:
> The thermal pressure signal gives information to the scheduler about
> reduced CPU capacity due to thermal. It is based on a value stored in a
> per-cpu 'thermal_pressure' variable. The online CPUs will get the new
> value there, while the offline won't. Unfortunately, when the CPU is back
> online, the value read from per-cpu variable might be wrong (stale data).
> This might affect the scheduler decisions, since it sees the CPU capacity
> differently than what is actually available.
> 
> Fix it by making sure that all online+offline CPUs would get the proper
> value in their per-cpu variable when thermal framework sets capping.
> 
> Fixes: f12e4f66ab6a3 ("thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping")
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>  drivers/thermal/cpufreq_cooling.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
> index eeb4e4b76c0b..43b1ae8a7789 100644
> --- a/drivers/thermal/cpufreq_cooling.c
> +++ b/drivers/thermal/cpufreq_cooling.c
> @@ -478,7 +478,7 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
>  	ret = freq_qos_update_request(&cpufreq_cdev->qos_req, frequency);
>  	if (ret >= 0) {
>  		cpufreq_cdev->cpufreq_state = state;
> -		cpus = cpufreq_cdev->policy->cpus;
> +		cpus = cpufreq_cdev->policy->related_cpus;
>  		max_capacity = arch_scale_cpu_capacity(cpumask_first(cpus));
>  		capacity = frequency * max_capacity;
>  		capacity /= cpufreq_cdev->policy->cpuinfo.max_freq;

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh