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

From: Rafael J. Wysocki
Date: Mon Dec 18 2017 - 06:35:40 EST

On Mon, Dec 18, 2017 at 5:59 AM, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> On 17-12-17, 01:19, Rafael J. Wysocki wrote:
>> 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?
> I didn't like adding scheduling class specific flags, and wanted the code to
> treat all of them in the same way. And then the governors can make a policy over
> that, on what to ignore and what not to. For example with the current patchset,
> the governors can know when nothing else is queued on a CPU and CPU is going to
> get into idle loop. They can choose to (or not to) do something in that case.

Well, if SCHED_CPUFRREQ_CLEAR means "this CPU is going to enter the
idle loop" really, then it is better to call it

SCHED_CPUFRREQ_CLEAR meaning basically "you should clear these flags
now" doesn't seem to convey any information to whoever doesn't
squirrel the flags in the first place.