On the implementation of dependable real-time systems with non-preemptive EDF

Abstract

Non-preemptive schedulers remain a very popular choice for practitioners of resource constrained real-time embedded systems. This chapter is concerned with the non-preemptive version of the Earliest Deadline First algorithm (npEDF). Although several key results indicate that npEDF should be considered a viable choice for use in resource-constrained real-time systems, these systems have traditionally been implemented using static, table-driven approaches such as the 'cyclic executive'. This is perhaps due to several popular misconceptions regarding the basic operation, optimality and robustness of this algorithm. This chapter will attempt to redress this balance by showing that many of the supposed 'problems' attributed to npEDF can be easily overcome by adopting appropriate implementation and analysis techniques. Examples are given to highlight the fact that npEDF generally outperforms other non-preemptive software architectures when scheduling periodic and sporadic tasks. The chapter concludes with the observation that npEDF should in fact be considered as the algorithm of choice for such systems. © 2011 Springer Science+Business Media B.V.