Re: [PATCH v5 08/10] cpufreq/schedutil: take into account interrupt

Juri Lelli
2018-05-28T12:37:40Z

On 28/05/18 14:06, Vincent Guittot wrote:
> Hi Juri,
>
> On 28 May 2018 at 12:41, Juri Lelli <juri.lelli@redhat.com> wrote:
> > Hi Vincent,
> >
> > On 25/05/18 15:12, Vincent Guittot wrote:
> >> The time spent under interrupt can be significant but it is not reflected
> >> in the utilization of CPU when deciding to choose an OPP. Now that we have
> >> access to this metric, schedutil can take it into account when selecting
> >> the OPP for a CPU.
> >> The CPU utilization is :
> >> irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
> >
> > IIUC the code below you actually propose that
> >
> > util = [(max_cap - util_irq) * util_rq] / max_cap + util_irq
> >
> > where
> >
> > util_rq = /Sum rq util_avg
> > util_irq = irq util_avg
> >
> > So, which one is what you have in mind? Or am I wrong? :)
>
> mmh ... aren't they equal ?
>
> util = [(max_cap - util_irq) * util_rq] / max_cap + util_irq
> util = [(max_cap/max_cap - util_irq/max_cap) * util_rq] + util_irq
> util = [(1 - util_irq/max_cap) * util_rq] + util_irq
> util = util_irq + [(1 - util_irq/max_cap) * util_rq]

Ah, indeed.