RE: [RFC PATCH v3 2/2] cpuidle: teo: Introduce util-awareness

[Doug Smythies]

On 2022.11.25 10:27 Rafael wrote:
> On Mon, Oct 31, 2022 at 1:14 PM Kajetan wrote:

... [delete some] ...

>> +}
>> +
>> /**
>>   * teo_update - Update CPU metrics after wakeup.
>>   * @drv: cpuidle driver containing state data.
>> @@ -303,7 +359,9 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
>>         int i;
>>
>>         if (dev->last_state_idx >= 0) {
>> -               teo_update(drv, dev);
>> +               /* don't update metrics if the cpu was utilized during the last sleep */
>
> Why?
>
> The metrics are related to idle duration and cpu_data->utilized
> indicates whether or not latency should be reduced.  These are
> different things.
>
> Moreover, this is just one data point and there may not be any direct
> connection between it and the decision made in this particular cycle.

Hi Rafael,

Yes, agreed. And version 4 of this patch set deleted this stuff.
See also my similar feedback, with accompanying test data
that verified the issue in [1].

[1] https://lore.kernel.org/linux-pm/CAAYoRsUgm6KyJCDowGKFVuMwJepnVN8NFEenjd3O-FN7+BETSw@xxxxxxxxxxxxxx/

... Doug