Task parameter computations for constraint deadline real-time systems with EDF scheduling

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 task relative deadline and period (interarrival time) can be made to a task that will deliver a schedulable system. In this paper, we address the sensitivity analysis (task parameter computations) of relative deadline and period for EDF scheduled systems on a uniprocessor when the ratio of deadline to period is a fixed value. We show that a task relative deadline and period which will result in a system that is borderline schedulable 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 computations are therefore as efficient as QPA, and are easily incorporated into a system design support tool.