EMA C++ Performace Tools Guide : 2 Open Source Performance Tool Suite Overview : 2.4 What Is Measured and Reported : 2.4.4 CPU & Memory Usage
 
2.4.4 CPU & Memory Usage
Performance tools record a periodic sampling of CPU and Memory usage. This allows for consistent monitoring of resource use and can be used to determine the impact of various features and application modifications.
The CPU and Memory Usage calculations represent the process as a whole, and are not normalized to the number of CPU cores nor running threads. All threads in each tool contribute to the overall execution time; it is possible for the reported CPU usage to be greater than 100% if the application runs multiple busy threads.