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References: <20231129110853.94344-1-lukasz.luba@arm.com> <20231129110853.94344-10-lukasz.luba@arm.com>
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From: Xuewen Yan <xuewen.yan94@gmail.com>
Date: Tue, 19 Dec 2023 12:03:28 +0800
Message-ID: <CAB8ipk_5TjUTrZ-nrGAwYMugLJFF72MvvRDzPJqaCayNwCm1wg@mail.gmail.com>
Subject: Re: [PATCH v5 09/23] PM: EM: Use runtime modified EM for CPUs energy
 estimation in EAS
To: Qais Yousef <qyousef@layalina.io>
Cc: Lukasz Luba <lukasz.luba@arm.com>, linux-kernel@vger.kernel.org, 
	linux-pm@vger.kernel.org, rafael@kernel.org, dietmar.eggemann@arm.com, 
	rui.zhang@intel.com, amit.kucheria@verdurent.com, amit.kachhap@gmail.com, 
	daniel.lezcano@linaro.org, viresh.kumar@linaro.org, len.brown@intel.com, 
	pavel@ucw.cz, mhiramat@kernel.org, wvw@google.com
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On Mon, Dec 18, 2023 at 1:59=E2=80=AFAM Qais Yousef <qyousef@layalina.io> w=
rote:
>
> On 11/29/23 11:08, Lukasz Luba wrote:
> > The new Energy Model (EM) supports runtime modification of the performa=
nce
> > state table to better model the power used by the SoC. Use this new
> > feature to improve energy estimation and therefore task placement in
> > Energy Aware Scheduler (EAS).
>
> nit: you moved the code to use the new runtime em table instead of the on=
e
> parsed at boot.
>
> >
> > Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
> > ---
> >  include/linux/energy_model.h | 16 ++++++++++++----
> >  1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/energy_model.h b/include/linux/energy_model.=
h
> > index 1e618e431cac..94a77a813724 100644
> > --- a/include/linux/energy_model.h
> > +++ b/include/linux/energy_model.h
> > @@ -238,6 +238,7 @@ static inline unsigned long em_cpu_energy(struct em=
_perf_domain *pd,
> >                               unsigned long max_util, unsigned long sum=
_util,
> >                               unsigned long allowed_cpu_cap)
> >  {
> > +     struct em_perf_table *runtime_table;
> >       unsigned long freq, scale_cpu;
> >       struct em_perf_state *ps;
> >       int cpu, i;
> > @@ -255,7 +256,14 @@ static inline unsigned long em_cpu_energy(struct e=
m_perf_domain *pd,
> >        */
> >       cpu =3D cpumask_first(to_cpumask(pd->cpus));
> >       scale_cpu =3D arch_scale_cpu_capacity(cpu);
> > -     ps =3D &pd->table[pd->nr_perf_states - 1];
> > +
> > +     /*
> > +      * No rcu_read_lock() since it's already called by task scheduler=
.
> > +      * The runtime_table is always there for CPUs, so we don't check.
> > +      */
>
> WARN_ON(rcu_read_lock_held()) instead?

I agree, or SCHED_WARN_ON(!rcu_read_lock_held()) ?

>
>
> Cheers
>
> --
> Qais Yousef
>
> > +     runtime_table =3D rcu_dereference(pd->runtime_table);
> > +
> > +     ps =3D &runtime_table->state[pd->nr_perf_states - 1];
> >
> >       max_util =3D map_util_perf(max_util);
> >       max_util =3D min(max_util, allowed_cpu_cap);
> > @@ -265,9 +273,9 @@ static inline unsigned long em_cpu_energy(struct em=
_perf_domain *pd,
> >        * Find the lowest performance state of the Energy Model above th=
e
> >        * requested frequency.
> >        */
> > -     i =3D em_pd_get_efficient_state(pd->table, pd->nr_perf_states, fr=
eq,
> > -                                   pd->flags);
> > -     ps =3D &pd->table[i];
> > +     i =3D em_pd_get_efficient_state(runtime_table->state, pd->nr_perf=
_states,
> > +                                   freq, pd->flags);
> > +     ps =3D &runtime_table->state[i];
> >
> >       /*
> >        * The capacity of a CPU in the domain at the performance state (=
ps)
> > --
> > 2.25.1
> >
>