Viresh Kumar [off-list ref] writes:

On 21-02-16, 22:33, Arto Jantunen wrote:

quoted

I have tested both available governors, and see the same behavior either
way. The kernel I have defaults to performance, I think I'll try
building another one which defaults to powersave to see if that changes
anything (perhaps both governors actually work but it isn't possible to
switch between them at runtime?). The Debian userspace defaults to
ondemand, which doesn't exist for intel_pstate.

I took a close look at git log between 4.4 and 4.5-rc1 for intel-pstate and it
had only three patches:

157386b6fc14 cpufreq: intel_pstate: Configurable algorithm to get target pstate
e70eed2b6454 cpufreq: intel_pstate: Account for non C0 time
63d1d656a523 cpufreq: intel_pstate: Account for IO wait time

The first one creates special routines based on the CPU model you have, yours is
94, i.e. 5e, which means we are going to use: core_params in your case. And so
you will be using get_target_pstate_use_performance() for .get_target_pstate().

The two later patches doesn't make any changes to the working of core_params()
and so shouldn't have changed anything for skylake.

Anyway, Please trying reverting the above three patches to see if there is a bug
somewhere there. So you need to do:

git revert 63d1d656a523
git revert e70eed2b6454
git revert 157386b6fc14

Thanks. I tried this, and somewhat surprisingly it doesn't change the
result. I guess we are back to doing a full bisect?

-- 
Arto Jantunen