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SubjectRe: [RFC PATCH 1/7] PM: Introduce em_pd_get_higher_freq()
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.

> Thanks,
> Quentin

--
#include <best/regards.h>

Patrick Bellasi

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