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

[SergeyKostrov]

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

[SergeyKostrov]

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

[Peter_W_Intel]

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

[Bernard]

>>>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.

[SergeyKostrov]

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?

[Bernard]

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.