Online workload monitoring with the feedback of actual execution time for real-time systems

Guaranteeing the system workload within design bounds is a basic requirement for a real-time system. Design-time bounds are usually based on worst-case activation patterns and worst-case execution time. While using the worst-case assumptions for online monitoring can guarantee the system safety, it also introduces unexplored slacks due to tasks consuming less than their worst-case execution times. In this paper, we introduce a monitoring scheme with the feedback of actual execution time for real-time systems. By using this runtime feedback instead of offline assumptions, this monitoring scheme can accept events that are considered as violations offline, and thereby improve the system utilization. In the experiments of both MATLAB simulation and MicroC/OS-II running in a softcore processor implemented on an FPGA, different probability distributions of actual execution time are used in analyzing how much the benefit can be gained from the feedback scheme.