Sensitivity Analysis for EDF Scheduled Arbitrary Deadline Real-Time Systems

The correctness of a real-time system depends on not only the system's output but also on the time at which results are produced. A hard real-time system is required to complete its operations before all its timing deadlines. For a given task set it is useful to know what is the minimum speed of the processor that will deliver a schedulable system. It is also beneficial in an engineering context to know what changes to computation time can be made to a task that will result in a system that is borderline schedulable. In this paper, we address the sensitivity analysis (parameter calculations) for task execution times and speed of the processor for EDF-scheduled systems on a uniprocessor. We prove that an optimal (minimum or maximum) task parameter can be determined by a single pass of the QPA algorithm. This algorithm provides efficient and exact sensitivity analysis for arbitrary deadline real-time systems. The approaches developed for task parameter computations are therefore as efficient as QPA, and are easily incorporated into a system design support tool.