Re: [PATCH v4] sched/freq: move call to cpufreq_update_util

[Peter Zijlstra]

On Fri, Nov 15, 2019 at 12:03:31PM +0100, Vincent Guittot wrote:
> On Fri, 15 Nov 2019 at 11:51, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >
> > On Fri, Nov 15, 2019 at 11:46:01AM +0100, Vincent Guittot wrote:
> > > On Fri, 15 Nov 2019 at 11:37, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >
> > > > Sure, but then it can still remember the value passed in last and use
> > > > that state later.
> > > >
> > > > It doesn't _have_ to completely discard values.
> > >
> > > yes but it means that we run at the "wrong" frequency during this
> > > period and also that the cpufreq must in this case set a kind of timer
> > > to resubmit a new frequency change out of scheduler event
> >
> > But if, as you say, we're completely shutting down the event stream
> > when everything has decayed, that's still true, right?
> 
> But It doesn't because there is nothing else to do.
> 
> This patch does 2 things:
> - fix the spurious call to cpufreq just before attaching a task
> - make sure cpufreq is still called when cfs is 0 but not irq/rt or dl
> 
> There are somehow related but not fully

Right, but when everything is 0, we stop generating events because we
stop calling update_blocked_average(), so there will be a last event
when we hit all 0s and then nothing.

So no superfluous events.

And if that last event if thrown out because of rate-limiting ....