Re: Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq

Andreas Herrmann
2018-07-17T09:11:52Z

On Tue, Jul 17, 2018 at 11:06:29AM +0200, Rafael J. Wysocki wrote:
> On Tue, Jul 17, 2018 at 10:50 AM, Andreas Herrmann <aherrmann@suse.com> wrote:
>
> [cut]
>
> >
> > On balance before this commit users could use pcc-cpufreq but had
> > already suboptimal performance (compared to say intel_pstate driver
> > which can be used changing BIOS options).
>
> BTW, I wonder why you need to change the BIOS options for intel_pstate to load.

I think this is because of (in intel_pstate_init()):

/*
* The Intel pstate driver will be ignored if the platform
* firmware has its own power management modes.
*/
if (intel_pstate_platform_pwr_mgmt_exists())
return -ENODEV;

> It should be initialized before pcc-cpufreq (according to their
> respective initcall levels), so in theory intel_pstate should be used
> by default on the affected systems anyway.

> What BIOS settings need to be changed for that?

Already answered in other mail.

Andreas