Messages in this thread | | | Date | Fri, 21 Jun 2019 11:22:03 +0100 | From | Quentin Perret <> | Subject | Re: [RFC PATCH 1/7] PM: Introduce em_pd_get_higher_freq() |
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On Friday 21 Jun 2019 at 11:17:05 (+0100), Quentin Perret wrote: > On Thursday 20 Jun 2019 at 14:04:39 (+0100), Patrick Bellasi wrote: > > On 19-Jun 17:08, Douglas Raillard wrote: > > > Hi Patrick, > > > > > > On 5/16/19 2:22 PM, Patrick Bellasi wrote: > > > > On 16-May 14:01, Quentin Perret wrote: > > > > > On Thursday 16 May 2019 at 13:42:00 (+0100), Patrick Bellasi wrote: > > > > > > > +static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd, > > > > > > > + unsigned long min_freq, unsigned long cost_margin) > > > > > > > +{ > > > > > > > + unsigned long max_cost = 0; > > > > > > > + struct em_cap_state *cs; > > > > > > > + int i; > > > > > > > + > > > > > > > + if (!pd) > > > > > > > + return min_freq; > > > > > > > + > > > > > > > + /* Compute the maximum allowed cost */ > > > > > > > + for (i = 0; i < pd->nr_cap_states; i++) { > > > > > > > + cs = &pd->table[i]; > > > > > > > + if (cs->frequency >= min_freq) { > > > > > > > + max_cost = cs->cost + (cs->cost * cost_margin) / 1024; > > > > > > ^^^^ > > > > > > ... end here we should probably better use SCHED_CAPACITY_SCALE > > > > > > instead of hard-coding in values, isn't it? > > > > > > > > > > I'm not sure to agree. This isn't part of the scheduler per se, and the > > > > > cost thing isn't in units of capacity, but in units of power, so I don't > > > > > think SCHED_CAPACITY_SCALE is correct here. > > > > > > > > Right, I get the units do not match and it would not be elegant to use > > > > it here... > > > > > > > > > But I agree these hard coded values (that one, and the 512 in one of the > > > > > following patches) could use some motivation :-) > > > > > > > > ... ultimately SCHED_CAPACITY_SCALE is just SCHED_FIXEDPOINT_SCALE, > > > > which is adimensional. Perhaps we should use that or yet another alias > > > > for the same. > > > > > > Would it be a good idea to use SCHED_FIXEDPOINT_SCALE in energy.c ? > > > Since it's not part of the scheduler, maybe there is a scale covering a wider scope, > > > or we can introduce a similar ENERGY_FIXEDPOINT_SCALE in energy_model.h. > > > > Well, in energy_model.c we have references to "capacity" and > > "utilization" which are all SCHED_FIXEDPOINT_SCALE range values. > > That symbol is defined in <linux/sched.h> and we already pull > > in other <linux/sched/*> headers. > > > > So, to me it seems it's not unreasonable to say that we use scheduler > > related concepts and it makes more sense than introducing yet another > > scaling factor. > > > > But that's just my two cents ;) > > Perhaps use this ? > > https://elixir.bootlin.com/linux/latest/source/include/linux/energy_model.h#L43 >
Nah, bad idea actually ... Sorry for the noise
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