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

[Rafael J. Wysocki]

On Monday, January 13, 2020 1:29:11 PM CET Peter Zijlstra wrote:
> 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?

I'm not aware of any other at least as far as Intel chips go.