How is the measurement going to be triggered when this is deleted?

I'm still trying to figure this out, I'm not very familiar with Native AOT in general so I'd appreciate any suggestions

It looks like we would need to callYieldProcessorNormalization::PerformMeasurement() from here or add aEnsureYieldProcessorNormalizedInitialized() entry point to the new code that simply callsYieldProcessorNormalization::PerformMeasurement()

Do you happen to know if this function is called every ~4 seconds or faster than that? Currently we letYieldProcessorNormalization::PerformMeasurement() run every ~4 s so if that's the case, I believe we may add here the same call as in CoreCLR

if (YieldProcessorNormalization::IsMeasurementScheduled())    {GCX_PREEMP();YieldProcessorNormalization::PerformMeasurement();    }

FinalizerStart function is called once per process. It is equivalent ofFinalizerThreadStart function in regular CoreCLR.

I think you want to follow the same structure as in regular CoreCLR: Trigger the measurement from ScheduleMeasurementIfNecessary by callingRhEnableFinalization (it is equivalent ofFinalizerThread::EnableFinalization in regular CoreCLR) and then add the measurement to loop inProcessFinalizers().

Do you happen to know if this function is called every ~4 seconds or faster than that?

I am not sure. The whole deal with measuring duration of something that is proportional to CPU cycle is not very precise, since the CPU cycle can change drastically and many times per second and will be different for every core. Unless machine is configured into HighPerformance power plan, every measurement is a bit of a coin toss and will produce the same result with the same error margins.

The main purpose of calibration is to continue using historically hard-coded spin counts in numerous places where we spinwait while allowing that to work on systems with vastly different pause durations (i.e. on post-skylake intel CPUs pause takes ~140 cycles, pre-skylake is about ~10 cycles). For such purpose the callibration is precise enough.

I am not sure about the value of redoing the measurement over and over.
Perhaps to support scenarios where a VM is migrated between pre/post skylake machines.

I guess we can add a periodic call PerformMeasurement in NativeAOT and see what happens.

My guess - nothing will change, just a bit more time spent in PerformMeasurement.

There is value in having the same behavior though.
If the re-measuring (or the whole calibration deal) could be somehow avoided or improved, it would make sense to do for both runtimes.

IIRC there's a good reason to keep re-doing measurements, so probably keeping this behaviour in Native AOT would be better, I believe@kouvel or@mangod9 may elaborate better

The measurements done are very short and can be perturbed by CPU activity, the rolling min helps to stabilize it over time.