Re: [RFC][PATCH v2 2/2] cpufreq: schedutil: Avoid decreasing frequency of busy CPUs

[Peter Zijlstra]

On Tue, Mar 21, 2017 at 02:37:08PM +0100, Vincent Guittot wrote:
> On 21 March 2017 at 14:22, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> For the not overloaded case, it makes sense to immediately update to
> OPP to be aligned with the new utilization of the CPU even if it was
> not idle in the past couple of ticks

Yeah, but we cannot know. Also, who cares?

> > does exactly that. Note that the lack of idle time is an exact
> > equivalent of 100% utilized.
> >
> > So even while we cannot currently detect the 100% utilized state through
> > the running state tracking; because averages etc.. we can detect the
> > lack of idle time.
> 
> But after how much lack of idle time do we consider that we are overloaded ?

0 :-)

Note that utilization is an absolute metric, not a windowed one. That
is, there is no actual time associated with it. Now, for practical
purposes we end up using windowed things in many places,