Re: [PATCH v5 04/23] PM: EM: Refactor em_pd_get_efficient_state() to be more flexible

[Lukasz Luba]

On 12/12/23 18:49, Dietmar Eggemann wrote:
> On 29/11/2023 12:08, Lukasz Luba wrote:
> > The Energy Model (EM) is going to support runtime modification. There
> > are going to be 2 EM tables which store information. This patch aims
> > to prepare the code to be generic and use one of the tables. The function
> > will no longer get a pointer to 'struct em_perf_domain' (the EM) but
> > instead a pointer to 'struct em_perf_state' (which is one of the EM's
> > tables).
> I thought the 2 EM tables design is gone?
>
> IMHO it would be less code changes and hence a more enjoyable review
> experience if you would add the 'modifiable' feature to the existing EM
> (1) and not add (2) and then remove (1) in [21/23].

I have explained that to some other your email: such approach would
create a patch monster, touching all drivers and frameworks, to just
make sure they still can compile. This is not the right approach.


>   struct em_perf_domain {
> -	struct em_perf_state *table;                <-- (1)
>   	struct em_perf_table __rcu *runtime_table;  <-- (2)
>
> > Prepare em_pd_get_efficient_state() for the upcoming changes and
> > make it possible to re-use. Return an index for the best performance
>
> s/make it possible to re-use/make it possible to be re-used ?

OK

> > state for a given EM table. The function arguments that are introduced
> > should allow to work on different performance state arrays. The caller of
> > em_pd_get_efficient_state() should be able to use the index either
> > on the default or the modifiable EM table.
> >
> > Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>
> > Reviewed-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > ---
> >   include/linux/energy_model.h | 30 +++++++++++++++++-------------
> >   1 file changed, 17 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
> > index b9caa01dfac4..8069f526c9d8 100644
> > --- a/include/linux/energy_model.h
> > +++ b/include/linux/energy_model.h
> > @@ -175,33 +175,35 @@ void em_dev_unregister_perf_domain(struct device *dev);
> >   
> >   /**
> >    * em_pd_get_efficient_state() - Get an efficient performance state from the EM
> > - * @pd   : Performance domain for which we want an efficient frequency
> > - * @freq : Frequency to map with the EM
> > + * @state:		List of performance states, in ascending order
>
> (3)
>
> > + * @nr_perf_states:	Number of performance states
> > + * @freq:		Frequency to map with the EM
> > + * @pd_flags:		Performance Domain flags
> >    *
> >    * It is called from the scheduler code quite frequently and as a consequence
> >    * doesn't implement any check.
> >    *
> > - * Return: An efficient performance state, high enough to meet @freq
> > + * Return: An efficient performance state id, high enough to meet @freq
> >    * requirement.
> >    */
> > -static inline
> > -struct em_perf_state *em_pd_get_efficient_state(struct em_perf_domain *pd,
> > -						unsigned long freq)
> > +static inline int
> > +em_pd_get_efficient_state(struct em_perf_state *table, int nr_perf_states,
> > +			  unsigned long freq, unsigned long pd_flags)
>
> (3) but em_pd_get_efficient_state(struct em_perf_state *table
>                                                          ^^^^^
> [...]

Good catch, I'll change that.