Re: [PATCH 4/4] cpufreq: intel_pstate: enable boost for Skylake Xeon

[Peter Zijlstra]

On Mon, Jul 30, 2018 at 07:06:21AM -0700, Srinivas Pandruvada wrote:
> On Mon, 2018-07-30 at 14:16 +0300, Eero Tamminen wrote:
> > Questions:
> > 
> > * Does currently kernel CPU freq management have any idea which IO
> >    devices share TDP with the CPU cores?

> No. The requests we do to hardware is just indication only (HW can
> ignore it). The HW has a bias register to adjust and distribute power
> among users.
> We can have several other active device on servers beside CPU which
> when runs need extra power. So the HW arbitrates power.

That's not entirely accurate AFAIK. "No" is accurate for Intel, but the
ARM people have their IPA thing (not a beer):

  https://developer.arm.com/open-source/intelligent-power-allocation

  drivers/thermal/power_allocator.c

which IIUC interacts with their cpufreq driver to disallow certain OPP
states.

And note that I discourage intel_pstate active mode.