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 : 2.4.4.1 CPU Usage Calculation
 
2.4.4.1 CPU Usage Calculation
CPU Usage is calculated by periodically querying the OS for applications’ “busy” and “overall” times. The difference from the previous value is used to calculate an average CPU usage for each interval and presented as a percentage: