Sensitivity analysis of relative deadline for EDF scheduled 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 very useful in an engineering context to know what changes to relative deadline can be made to a task that will deliver a schedulable system. In this paper, we address the sensitivity analysis (parameter calculations) of task relative deadline for EDF scheduled systems on a uniprocessor. We prove that a minimum task relative deadline can be determined by a single pass of the QPA algorithm. This algorithm provides exact and efficient sensitivity analysis for arbitrary deadline real-time systems. The approaches developed for task parameter calculations are therefore as efficient as QPA, and are easily incorporated into a system design support tool.