Problem: CPU time for Hotspots or Threading Analysis is Too Low

Cause

The CPU time is low for one of the following reasons:

  • The analysis run was very short and the target consumed little CPU time.

  • CPU time may be inaccurate for targets that work in short quanta less than the scheduler tick interval. For example, this can happen for frame-by-frame computation in video decoders. To capture CPU time more accurately on Windows* OS, you need to run the analysis with the accurate CPU time detection mode enabled.

Solution

Try one of the following:

  • Extend the duration of the analysis run.

  • Windows OS only: Enable accurate CPU time detection. To do this for the Hotspots or Threading analysis, it is enough to run the VTune Amplifier with administrative permissions. You may also enable this option explicitly in the custom analysis configuration by checking the Collect highly accurate CPU time box. Make sure to extend maximum size of raw collector data.

Note

Accurate CPU time collection produces a significant amount of temporary data depending on the system configuration and the profiled target. VTune Amplifier may generate up to 5 Mb of temporary data per minute per logical CPU.

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