https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944013#M7735 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? Thu, 08 Nov 2012 13:48:25 GMT SergeyKostrov 2012-11-08T13:48:25Z https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944009#M7731 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 Thu, 08 Nov 2012 01:51:53 GMT https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944009#M7731 SergeyKostrov 2012-11-08T01:51:53Z https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944010#M7732 Actually, I don't details and I simply need Yes or No answer, like 'Yes, RDTSC used' or 'No, RDTSC Not used'... Thu, 08 Nov 2012 03:29:23 GMT https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944010#M7732 SergeyKostrov 2012-11-08T03:29:23Z https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944011#M7733 The answer is "No", VTune(TM) Amplifier retrieves the performance data from hardware PMU resource, via device drivers. Thu, 08 Nov 2012 08:17:00 GMT https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944011#M7733 Peter_W_Intel 2012-11-08T08:17:00Z https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944012#M7734 >>>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. Thu, 08 Nov 2012 12:14:29 GMT https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944012#M7734 Bernard 2012-11-08T12:14:29Z https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944013#M7735 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? Thu, 08 Nov 2012 13:48:25 GMT https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944013#M7735 SergeyKostrov 2012-11-08T13:48:25Z https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944014#M7736 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. Thu, 08 Nov 2012 20:03:46 GMT https://community.intel.com/t5/Analyzers/Does-VTune-use-QueryPerformanceCounter-Win32-API-function-or/m-p/944014#M7736 Bernard 2012-11-08T20:03:46Z