Collecting Highly Accurate CPU Time Data

Configure the Intel® VTune™ Amplifier to get highly accurate CPU time data in the user-mode sampling and tracing results.

By default, the VTune Amplifier detects CPU time based on the OS scheduler tick granularity. As a result, the CPU time values may be inaccurate for targets that execute in short quanta less than the OS scheduler tick interval (for example, frame-by-frame computation in video decoders).

Accurate collection of CPU time information is available for the user-mode sampling and tracing analysis types (Basic Hotspots , Concurrency , and Locks and Waits) and enabled by default in the predefined analysis configurations. You may disable this option by creating a new custom analysis based on the user-mode sampling and tracing collection.

This type of collection takes more processing time and disk space. VTune Amplifier may generate up to 5 MB of temporary data per minute per logical CPU depending on the system configuration and the profiled target.

To collect accurate CPU time information, you need to run both the VTune Amplifier and your application to analyze with administrator privileges.

VTune Amplifier needs exclusive access to the Microsoft* NT Kernel Logger. Therefore, only one VTune Amplifier collection can run in this mode on the system and no other tools can use the service. If the VTune Amplifier cannot get access to the NT Kernel Logger, the collection will continue with this mode disabled.

For more complete information about compiler optimizations, see our Optimization Notice.