Re: [RFC PATCH 0/7] Introduce thermal pressure

[Quentin Perret]

On Wednesday 10 Oct 2018 at 14:50:33 (+0200), Juri Lelli wrote:
> On 10/10/18 14:34, Vincent Guittot wrote:
> > Hi  Juri,
> > 
> > On Wed, 10 Oct 2018 at 14:23, Juri Lelli <juri.lelli@xxxxxxxxx> wrote:
> > >
> > > On 10/10/18 14:04, Vincent Guittot wrote:
> > >
> > > [...]
> > >
> > > > The problem was the same with RT, the cfs utilization was lower than
> > > > reality because RT steals soem cycle to CFS
> > > > So schedutil was selecting a lower frequency when cfs was running
> > > > whereas the CPU was fully used.
> > > > The same can happen with thermal:
> > > > cap the max freq because of thermal
> > > > the utilization with decrease.
> > > > remove the cap
> > > > the utilization is still low and you will select a low OPP because you
> > > > don't take into account cycle stolen by thermal like with RT
> > >
> > > What if we scale frequency component considering the capped temporary
> > > max?
> > 
> > Do you mean using a kind of scale_thermal_capacity in accumulate_sum
> > when computing utilization ?
> 
> Yeah, something like that I guess. So that we account for temporary
> "fake" 1024..

But wouldn't that break frequency invariance ? A task would look bigger
on a capped CPU than a non-capped one no ?