Priority Assignment for Global Fixed Priority Scheduling on Multiprocessors

Global fixed-priority (G-FP) scheduling is a widely applied scheduling policy for real-time systems running on multiprocessor platforms. The state-of-the-art in priority assignment for G-FP follows one of two approaches. The first is to use a simple heuristic for priority assignment that works with any (thus the most accurate) schedulability analysis. The second is to leverage Audsley's polynomial-time optimal priority assignment (OPA) algorithm, which can only accommodate a less accurate analysis that satisfies the compatibility conditions required by OPA. In this article, we study this critical issue and present a novel algorithm. We first use the concept of response time estimation range to build a new priority assignment framework, which is optimal with a more accurate schedulability analysis than OPA since its compatibility conditions are much weaker than those of OPA. This new frontier on the second approach is then judiciously combined with the first approach to take advantage of both. We evaluate the effectiveness of the proposed algorithm with various task sets. Compared with existing approaches, our algorithm always achieves the highest-acceptance ratio and can outperform them by 25% on average.