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

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

Ritratto di Sergey Kostrov
Sergey Kostrov
Mer, 07/11/2012 - 17:51

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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Ritratto di Sergey Kostrov
Sergey Kostrov
Mer, 07/11/2012 - 19:29

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

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Ritratto di Peter Wang (Intel)
Peter Wang (Intel)
Gio, 08/11/2012 - 00:17

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

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Ritratto di iliyapolak
iliyapolak
Gio, 08/11/2012 - 04:14

>>>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.

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Ritratto di Sergey Kostrov
Sergey Kostrov
Gio, 08/11/2012 - 05:48

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?

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Ritratto di iliyapolak
iliyapolak
Gio, 08/11/2012 - 12:03

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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