Messages in this thread | | | Date | Tue, 10 Apr 2018 14:56:41 +0100 | From | Quentin Perret <> | Subject | Re: [RFC PATCH v2 4/6] sched/fair: Introduce an energy estimation helper function |
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On Tuesday 10 Apr 2018 at 14:51:05 (+0200), Peter Zijlstra wrote: > On Fri, Apr 06, 2018 at 04:36:05PM +0100, Dietmar Eggemann wrote: > > +static inline > > +struct capacity_state *find_cap_state(int cpu, unsigned long util) > > +{ > > + struct sched_energy_model *em = *per_cpu_ptr(energy_model, cpu); > > + struct capacity_state *cs = NULL; > > + int i; > > + > > + util += util >> 2; > > + > > + for (i = 0; i < em->nr_cap_states; i++) { > > + cs = &em->cap_states[i]; > > + if (cs->cap >= util) > > + break; > > + } > > + > > + return cs; > > +} > > So in the last thread there was some discussion about this; in > particular on how this related to schedutil and if we should tie it into > that. > > I think for starters tying it to schedutil is not a bad idea; ideally > people _should_ migrate towards using that. > > Also; I think it makes sense to better integrate cpufreq and the > energy-model values like what rjw already suggested, such that maybe we > can have cpufreq_driver_resolve_freq() return a structure containing the > relevant information for the selected frequency.
I guess if we want to do that in the wake-up path, we would also need to add a new parameter to it to make sure we don't actually call into cpufreq_driver->resolve_freq() ...
But then, we could sort of rely on cpufreq_schedutil.c::get_next_freq() to replace find_cap_state() ... Is this what you had in mind ?
> > But implementing the frequency selection thing in multiple places like > now sounds like a very bad idea to me.
Understood. Making sure we share the same code everywhere might have consequences though. I guess we'll have to either accept the cost of function calls in the wake-up path, or to accept to inline those functions for ex. Or maybe you had something else in mind ?
Anyways, that's probably another good discussion topic for OSPM next week :-)
Thanks, Quentin
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