Re: [PATCH v2 1/4] PM / EM: add devices to Energy Model

[Lukasz Luba]

On 2/13/20 10:59 AM, Dietmar Eggemann wrote:
> On 06/02/2020 14:46, lukasz.luba@xxxxxxx wrote:
> > From: Lukasz Luba <lukasz.luba@xxxxxxx>
>
> [..]
>
> > @@ -26,7 +28,7 @@ framework, and interested clients reading the data from it::
>
> s/::/: ?
>
> >          | Thermal (IPA) |  | Scheduler (EAS) |  |     Other     |
> >          +---------------+  +-----------------+  +---------------+
> >                  |                   | em_pd_energy()    |
> > -               |                   | em_cpu_get()      |
> > +               |  em_get_pd()      | em_cpu_get()      |
> >                  +---------+         |         +---------+
>
> em_get_pd() and em_cpu_get()? Why not em_pd_get()? em_cpu_get() is a
> specific em_get_pd(). right?

Yes. I will rename 'em_get_pd' to 'em_pd_get'

> [...]
>
> > @@ -85,13 +89,20 @@ API.
> >   2.3 Accessing performance domains
> >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >   
> > +There is two API functions which provide the access to the energy model:
> > +em_cpu_get() which takes CPU id as an argument and em_get_pd() with device
> > +pointer as an argument. It depends on the subsystem which interface it is
> > +going to use, but in case of CPU devices both functions return the same
> > +performance domain.
>
> There is probably a reason why we need this specific function for CPU
> devices? The reason should be described. People might ask why
> em_get_pd() is not sufficient.

True, good point. I will extend the comment in em_cpu_get().

> [...]
>
> > - * A "performance domain" represents a group of CPUs whose performance is
> > - * scaled together. All CPUs of a performance domain must have the same
> > - * micro-architecture. Performance domains often have a 1-to-1 mapping with
> > - * CPUFreq policies.
> > + * In case of CPU device, a "performance domain" represents a group of CPUs
> > + * whose performance is scaled together. All CPUs of a performance domain
> > + * must have the same micro-architecture. Performance domains often have
> > + * a 1-to-1 mapping with CPUFreq policies.
> > + * In case of other devices the 'priv' field is unused.
> >    */
> >   struct em_perf_domain {
> > -	struct em_cap_state *table;
> > -	int nr_cap_states;
> > -	unsigned long cpus[0];
> > +	struct em_perf_state *table;
> > +	int nr_perf_states;
> > +	void *priv;
>
> In case you go back to the variable length field plus type field to
> distingush EM devices, keep cpus[0] as the name.

OK, I will.

> [..]
>
> >   /**
> > - * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf. domain
> > + * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf.
> > +			domain
>
> Why this change?

hmmm, that's odd, maybe there was 'device' then I changed it back to
'CPUs' but forgot to move the 'domain' to the old place.

> [...]
>
> > @@ -141,12 +210,12 @@ static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
> >   		 */
> >   		opp_eff = freq / power;
> >   		if (opp_eff >= prev_opp_eff)
> > -			pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
> > -					cpu, i, i - 1);
> > +			dev_warn(dev, "energy_model: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
>
> s/energy_model/EM ?

OK, I will rename them in all places.

Thank you for the review.

Regards,
Lukasz