On Thu, Dec 3, 2020 at 1:42 PM Peter Zijlstra <pet...@infradead.org> wrote:
>
> On Mon, Nov 30, 2020 at 07:37:01PM +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
> >
> > First off, some cpufreq drivers (eg. intel_pstate) can pass hints
> > beyond the current target frequency to the hardware and there are no
>
> Everything CPPC, which is quite a bit these days.
Right, but that is still "some". :-) I can add it to the list of
examples, though.
> > + /*
> > + * ->fast_switch() replacement for drivers that use an internal
> > + * representation of performance levels and can pass hints other than
> > + * the target performance level to the hardware.
> > + */
> > + void (*adjust_perf)(unsigned int cpu, bool busy,
> > + unsigned long min_perf,
> > + unsigned long target_perf,
> > + unsigned long capacity);
> >
>
> I'm not sure @busy makes sense, that's more a hack because @util had a
> dip and should remain inside schedutil.
So I did it this way, because schedutil would need to store the old
value of target_perf for this and intel_pstate already does that.
But if a new util_hook is used in this case, the existing space in
sg_policy may be used for that.
> > @@ -454,6 +455,25 @@ static void sugov_update_single(struct u
> > util = sugov_get_util(sg_cpu);
> > max = sg_cpu->max;
> > util = sugov_iowait_apply(sg_cpu, time, util, max);
> > +
> > + /*
> > + * This code runs under rq->lock for the target CPU, so it won't run
> > + * concurrently on two different CPUs for the same target and it is
> > not
> > + * necessary to acquire the lock in the fast switch case.
> > + */
> > + if (sg_policy->direct_fast_switch) {
> > + /*
> > + * In this case, any optimizations that can be done are up to
> > + * the driver.
> > + */
> > + cpufreq_driver_adjust_perf(sg_cpu->cpu,
> > + sugov_cpu_is_busy(sg_cpu),
> > + map_util_perf(sg_cpu->bw_dl),
> > + map_util_perf(util), max);
> > + sg_policy->last_freq_update_time = time;
> > + return;
> > + }
>
> Instead of adding more branches, would it makes sense to simply set a
> whole different util_hook in this case?
Looks doable without too much code duplication. Lemme try.
