Messages in this thread | | | Subject | Re: [PATCH v2 3/3] PM / EM: Skip inefficient OPPs | From | Lukasz Luba <> | Date | Tue, 25 May 2021 14:34:12 +0100 |
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Hi Quentin,
On 5/25/21 2:06 PM, Quentin Perret wrote: > Hi Lukasz, > > On Tuesday 25 May 2021 at 12:03:14 (+0100), Lukasz Luba wrote: >> That's a few more instructions to parse the 'flags' filed. I'm not sure >> if that brings speed improvements vs. if we not parse and have bool >> filed with a simple looping. The out-of-order core might even suffer >> from this parsing and loop index manipulations... > > I'm not sure what you mean about parsing here? I'm basically suggesting > to do something along the lines of:
I thought Vincent was going to re-use the 'flags' for it and keep it for other purpose as well - which would require to parse/map-to-feature. That's why I commented the patch earlier, pointing out that we shouldn't prepare the code for future unknown EM_PERF_STATE_*. We can always modify it when we need to add another feature later.
> > diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h > index daaeccfb9d6e..f02de32d2325 100644 > --- a/include/linux/energy_model.h > +++ b/include/linux/energy_model.h > @@ -128,13 +128,11 @@ struct em_perf_state *em_pd_get_efficient_state(struct em_perf_domain *pd, > > for (i = 0; i < pd->nr_perf_states; i++) { > ps = &pd->table[i]; > - if (ps->flags & EM_PERF_STATE_INEFFICIENT) > - continue; > if (ps->frequency >= freq) > break; > } > > - return ps; > + return &pd->table[ps->next_efficient_idx]; > } > > What would be wrong with that?
Until we measure it, I don't know TBH. It looks OK for the first glance. I like it also because it's self-contained, doesn't require parsing, doesn't bring any 'generic' variable.
Regards, Lukasz
> > Thanks, > Quentin >
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