Re: [PATCH v2 14/17] Documentation: EM: Add a new section about the design

[Lukasz Luba]

On 5/30/23 11:33, Dietmar Eggemann wrote:
> On 12/05/2023 11:57, Lukasz Luba wrote:
> > Add a new section 'Design' which covers the information about Energy
> > Model. It contains the design decisions, describes models and how they
> > reflect the reality. Add description of the basic const. EM. Change the
> > other section IDs.
>
> I would vote for coalescing the 4 doc patches into 1.

OK, I can make that. I will be a big one patch, though.

> > Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>
> > ---
> >   Documentation/power/energy-model.rst | 36 +++++++++++++++++++++-------
> >   1 file changed, 27 insertions(+), 9 deletions(-)
> >
> > diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst
> > index ef341be2882b..e97c7f18d8bd 100644
> > --- a/Documentation/power/energy-model.rst
> > +++ b/Documentation/power/energy-model.rst
> > @@ -72,16 +72,34 @@ required to have the same micro-architecture. CPUs in different performance
> >   domains can have different micro-architectures.
> >   
> >   
> > -2. Core APIs
> > +2. Design
> > +-----------------
> > +
> > +2.1 Basic EM
> > +^^^^^^^^^^^^
>
> Can we make sure that people get the relation between 'basic' and
> 'default' easier?
>
> It should be obvious that `pd->default_table->state` refers to this
> `basic (const.) EM. Using the same identifier always helps in this
> situation.

OK, how about adding this:
"The basic EM is built around const. power information for each
performance state, which is accessible in:
'dev->em_pd->default_table->state'. This model can be derived based..."

> > +
> > +The basic EM is built around const. power information for each performance
> > +state. This model can be derived based on power measurements of the device
> > +e.g. CPU while running some benchmark. The benchmark might be integer heavy
> > +or floating point computation with a data set fitting into the CPU cache or
> > +registers. Bare in mind that this model might not be covering all possible
> > +workloads running on CPUs. Thus, please run a few different benchmarks and
> > +verify with some real workloads your power model values. The power variation
> > +due to the workload instruction mix and data set is not modeled.
> > +Also static power which can change during runtime due to variation of SOC
> > +temperature is not modeled in EM.
> > +
> > +