Re: [RFC 0/3] Introduce cpufreq minimum load QoS

[Vincent Guittot]

On Wed, 29 Apr 2020 at 17:50, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
>
> On Friday, April 24, 2020 1:40:55 PM CEST Benjamin Gaignard wrote:
> > When start streaming from the sensor the CPU load could remain very low
> > because almost all the capture pipeline is done in hardware (i.e. without
> > using the CPU) and let believe to cpufreq governor that it could use lower
> > frequencies. If the governor decides to use a too low frequency that
> > becomes a problem when we need to acknowledge the interrupt during the
> > blanking time.
> > The delay to ack the interrupt and perform all the other actions before
> > the next frame is very short and doesn't allow to the cpufreq governor to
> > provide the required burst of power. That led to drop the half of the frames.
> >
> > To avoid this problem, DCMI driver informs the cpufreq governors by adding
> > a cpufreq minimum load QoS resquest.
>
> This seems to be addressing a use case that can be addressed with the help of
> utilization clamps with less power overhead.

Can't freq_qos_update_request() be also used if you don't have cgroup
enabled on your system ?

>
> Thanks!
>
>
>