linux-kernel - Re: [Patch v5 5/6] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping

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Date:   Wed, 6 Nov 2019 12:28:31 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Dietmar Eggemann <dietmar.eggemann@....com>, mingo@...hat.com,
        peterz@...radead.org, ionela.voinescu@....com,
        vincent.guittot@...aro.org, rui.zhang@...el.com,
        edubezval@...il.com, qperret@...gle.com
Cc:     linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        javi.merino@...nel.org, daniel.lezcano@...aro.org
Subject: Re: [Patch v5 5/6] thermal/cpu-cooling: Update thermal pressure in
 case of a maximum frequency capping

On 11/06/2019 07:50 AM, Dietmar Eggemann wrote:
> On 05/11/2019 19:49, Thara Gopinath wrote:
> 
> [...]
> 
>> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
>> index 391f397..c65b7c4 100644
>> --- a/drivers/thermal/cpu_cooling.c
>> +++ b/drivers/thermal/cpu_cooling.c
>> @@ -218,6 +218,27 @@ static u32 cpu_power_to_freq(struct cpufreq_cooling_device *cpufreq_cdev,
>>  }
>>  
>>  /**
>> + * update_sched_max_capacity - update scheduler about change in cpu
>> + *				max frequency.
>> + * @cpus: list of cpus whose max capacity needs udating in scheduler.
>> + * @cur_max_freq: current maximum frequency.
>> + * @max_freq: highest possible frequency.
>> + */
>> +static void update_sched_max_capacity(struct cpumask *cpus,
>> +				      unsigned int cur_max_freq,
>> +				      unsigned int max_freq)
>> +{
>> +	int cpu;
>> +	unsigned long capacity;
>> +
>> +	for_each_cpu(cpu, cpus) {
>> +		capacity = cur_max_freq * arch_scale_cpu_capacity(cpu);
>> +		capacity /= max_freq;
>> +		update_thermal_pressure(cpu, capacity);
>> +	}
>> +}
>> +
>> +/**
> 
> Have you seen
> https://lore.kernel.org/r/2b19d7da-412c-932f-7251-110eadbef3e3@arm.com ?
Yes and have you seen this
https://lore.kernel.org/lkml/CAKfTPtCpZq61gQVpATtTdg5hDA+tP4bF6xPMsvHYUMoY+H-6FQ@mail.gmail.com/

this
https://lore.kernel.org/lkml/5DBB0FD4.8000509@linaro.org/

and this from Ionela (which is the basis for v5)
https://lore.kernel.org/lkml/20191101154612.GA4884@e108754-lin/

I stand by what I said earlier that I see no reason to take parsing of
the cpus into fair.c for this feature (this way this solution is more
generic and can be used from any other entity capping maximum cpu frequency)

> 
> Also the naming 'update_thermal_pressure()' is not really suitable for
> an external task scheduler interface. If I see this called in the
> cooling device code, I wouldn't guess that this is a task scheduler
> interface.

Do you have a name suggestion? When you say you don't like a name do
suggest a name so that I have an idea of what is it you are expecting.

> 
> [...]
> 


-- 
Warm Regards
Thara