Does VTune use 'QueryPerformanceCounter' Win32 API function or 'RDTSC' instruction?

Does VTune use 'QueryPerformanceCounter' Win32 API function or 'RDTSC' instruction?

Hi everybody,

I simply would like to know how VTune gets times. Does VTune use 'QueryPerformanceCounter' Win32 API function or 'RDTSC' instruction?

Thanks in advance.

Best regards,
Sergey

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Actually, I don't details and I simply need Yes or No answer, like 'Yes, RDTSC used' or 'No, RDTSC Not used'...

Peter Wang (Intel)的头像

The answer is "No", VTune(TM) Amplifier retrieves the performance data from hardware PMU resource, via device drivers.

iliyapolak的头像

>>>VTune(TM) Amplifier retrieves the performance data from hardware PMU resource, via device drivers. >>>
IIRC VTune drivers access MSR in order to collect performance PMU data.

Thank you.

>>...VTune(TM) Amplifier retrieves the performance data from hardware PMU resource...

What is accuracy of measuring different time events? A nanosecond, or more, or less?

iliyapolak的头像

What is accuracy of measuring different time events? A nanosecond, or more, or less?
Probably it could be meaured in bus(QPI)cycles and translated by the software to nanosecond accuracy.

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