Re: About dynamic switch to offload/nocb on non-server Intel machines

[Joel Fernandes <joel@joelfernandes.org>]

Alison, Nice to hear from you!

> On Fri, Jul 8, 2022 at 10:19 AM Joel Fernandes <joel@joelfernandes.org> wrote:
> >
> > Dear Paul and Frederic,
> >
> > Len Brown on CC provided a good idea in a meeting on using intel_pstate to
> > detect if device is a server or a consumer device.
> 
> 
> Robots are neither a server nor a consumer device.   Please let's not
> force industrial users of RT to choose between two inapt sets of
> configuration options.

I see your point.

> > Can we perhaps use this to trigger the offload/nocb mechanisms on consumer
> > devices / distros? I was thinking the dynamic offload and the "one kernel"
> > work that Frederic did can be trigger from such detection.
> >
> > It is true userspace can do the trigger, but maybe it is better to not leave
> > it to userspace so we'd save power on bad userspaces.
> >
> > Come to think of it, this can even be done at boot time if we can read the
> > below state early enough:
> >
> > > intel_pstate.c demonstrates how to detect a server when ACPI is present:
> > >
> > >
> > >
> > > #ifdef CONFIG_ACPI
> > >
> > >
> > >
> > > static bool intel_pstate_acpi_pm_profile_server(void)
> > >
> > > {
> > >
> > >         if (acpi_gbl_FADT.preferred_profile =3D=3D PM_ENTERPRISE_SERVER |=
> > |
> > >
> > >             acpi_gbl_FADT.preferred_profile =3D=3D PM_PERFORMANCE_SERVER)
> > >
> > >                 return true;
> > >
> > >
> > >
> > >         return false;
> > >
> > > }
> > >
> 
> 
> Robotics applications often rely on fairly "big iron" that is
> configured with CONFIG_CPU_FREQ_GOV_PERFORMANCE=y.   Servers and
> robotics are quite different use cases, so setting configuration that
> would be useful for servers whenever the CPU_FREQ_GOV_PERFORMANCE is
> selected would create a headache for many users.

Fair enough, I had to ask...

thanks,

 - Joel

> Best wishes,
> Alison Chaiken
> Aurora Innovation
> 
> 
> *That was a joke.