Re: [PATCH 2/4] sched: cpufreq: Keep track of cpufreq utilization update flags

From: Rafael J. Wysocki
Date: Sat Dec 16 2017 - 19:20:13 EST

On Saturday, December 16, 2017 5:47:07 PM CET Viresh Kumar wrote:
> On 16 December 2017 at 22:10, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> > On Wed, Dec 13, 2017 at 10:53 AM, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> >> +#define SCHED_CPUFREQ_CLEAR (1U << 31)
> >
> > I'm not thrilled by this, because schedutil is not the only user of
> > the flags and it's totally unclear what the other user(s) should do
> > when this is set.
> intel-pstate is the only other user of the IOWAIT flag, right? In order
> not to change the current behavior, we can update that to return early
> for now ?

We can do that in principle, but why should it return early? Maybe it's
a good time to update things, incidentally?

I actually don't like the SCHED_CPUFRREQ_CLEAR flag *concept* as it is very
much specific to schedutil and blatantly ignores everybody else.

Alternatively, you could add two flags for clearing SCHED_CPUFREQ_RT and
SCHED_CPUFREQ_DL that could just be ingored entirely by intel_pstate.

So, why don't you make SCHED_CPUFREQ_RT and SCHED_CPUFREQ_DL "sticky" until,
say, SCHED_CPUFREQ_NO_RT and SCHED_CPUFREQ_NO_DL are passed, respectively?