Efficient Algorithms for Schedulability Analysis and Priority Assignment of Fixed-Offset Periodic Tasksets

Fixed-priority scheduling is the most common scheduling algorithm used in industry practice. Imposing fixed task release offsets is an effective technique for improving schedulability by avoiding the critical instant when all tasks are released simultaneously. In this paper, we address the problem of schedulability analysis and priority assignment for a periodic taskset with fixed-priority preemptive scheduling, where tasks have fixed offset relationships relative to each other. For schedulability analysis, we present an efficient algorithm for computing busy/idle periods, and obtaining response times of all instances of a task τi in the feasibility interval once the priority-level-pi busy periods are determined. For priority assignment, we adopt Audsley’s Optimal Priority Assignment (OPA) algorithm, and present an efficient algorithm for incremental construction of priority-level-(k−1) busy periods by removing all instances of the task with priority k from the priority-level-k busy periods. Performance evaluation shows that our algorithms can result in significant performance improvements compared to existing techniques.