Re: [RFC 0/3] Introduce cpufreq minimum load QoS

[Valentin Schneider <valentin.schneider@arm.com>]

On 30/04/20 14:46, Benjamin GAIGNARD wrote:
>> That's not what I meant.
>>
>> I suppose that the interrupt processing in question takes place in
>> process context and so you may set the lower clamp on the utilization
>> of the task carrying that out.
>
> I have try to add this code when starting streaming (before the first
> interrupt) the frames from the sensor:
> const struct sched_attr sched_attr = {
>    .sched_util_min = 10000, /* 100% of usage */

Unless you play with SCHED_CAPACITY_SHIFT, the max should be 1024 -
i.e. SCHED_CAPACITY_SCALE. That's a really big boost, but that's for you to
benchmark.

>    .sched_flags = SCHED_FLAG_UTIL_CLAMP_MIN,
>   };
>
> sched_setattr(current, &sched_attr);
>
> I don't see any benefices maybe there is some configuration flags to set.
>
> How changing sched_util_min could impact cpufreq ondemand governor ?
> Does it change the value returned when the governor check the idle time ?
>

You'll have to use the schedutil governor for uclamp to have an effect. And
arguably that's what you should be using, unless something explicitly
prevents you from doing that.

>>
>> Alternatively, that task may be a deadline one.