Re: [PATCH RFC] sched/fair: Penalty the cfs task which executes mwait/hlt

[Peter Zijlstra]

On Mon, Jan 13, 2020 at 12:18:46PM +0100, Rafael J. Wysocki wrote:
> On Monday, January 13, 2020 11:43:14 AM CET Peter Zijlstra wrote:

> > Anyone, what will it take to get MPERF/TSC 'working' ?
> 
> The same thing that intel_pstate does.

But intel_pstate cheats, it has a FMS listing and possible 'interesting'
chips are excluded. For instance, Core2 has APERF/MPERF, but
intel_pstate does not support Core2.

Simlarly, intel_pstate does (obviously) not support AMD chips, even tho
those have APERF/MPERF.

Although I suppose Core2 doesn't have VMX and is therefore less
interesting, but then we'd need to gate the logic with something like:

	static_cpu_has(X86_FEATURE_APERFMPERF) &&
	(static_cpu_has(X86_FEATURE_VMX) || static_cpu_has(X86_FEATURE_SVM)

> Generally speaking, it shifts the mperf values by a number of positions
> depending on the CPU model, but that is 1 except for KNL.
> 
> See get_target_pstate().

I'm going to go out on a limb and guess that's the same KNL hack as
TurboStat has.

Is that really the only known case?