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

SergeyKostrov
Valued Contributor II
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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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SergeyKostrov
Valued Contributor II
452 Views
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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Peter_W_Intel
Employee
452 Views
The answer is "No", VTune(TM) Amplifier retrieves the performance data from hardware PMU resource, via device drivers.
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Bernard
Valued Contributor I
452 Views
>>>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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SergeyKostrov
Valued Contributor II
452 Views
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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Bernard
Valued Contributor I
452 Views
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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