The Preemptive Uniprocessor Scheduling of Mixed-Criticality Implicit-Deadline Sporadic Task Systems

Abstract

Abstract-Systems in many safety-critical application domains are subject to certification requirements. For any given system, however, it may be the case that only a subset of its functionality is safety-critical and hence subject to certification; the rest of the functionality is non safety critical and does not need to be certified, or is certified to a lower level of assurance. An algorithm called EDF-VD (for Earliest Deadline First with Virtual Deadlines) is described for the scheduling of such mixed-criticality task systems. Analyses of EDF-VD significantly superior to previously-known ones are presented, based on metrics such as processor speedup factor (EDF-VD is proved to be optimal with respect to this metric) and utilization bounds.

Mixed Critical Earliest Deadline First

“…[9] presents a high performance priority computation that dominates OCBP empirically. Note that [8,9] are not directly applicable to the problem studied in this paper as they are restricted to the periodic job model. FPM provides better results than fixed priority, but in general dynamic priority may be necessary for optimality.…”

“…The priority assignment of [13] applies OCBP to compute P T LO , thus having equivalent schedulability. [8] proposes a low-overhead online computation of priorities. [9] presents a high performance priority computation that dominates OCBP empirically.…”

“…The Own-Criticality Based Priority (OCBP) [7] is theoretically the best among all fixed-priority scheduling algorithms for MCS. Recent extensions of the fixed-priority policy perform a switch between different priority tables for different modes, showing in practice a significant improvement of schedulability, while still reusing a lot in terms of implementation and theory from the classical fixed job priority scheduling [8,9]. However, to the best of our knowledge none of such extended fixed-priority policies has ever been theoretically proven to dominate OCBP, despite their extra degree of freedom -to switch the priority tables.…”

Semi-partitioned Mixed-Criticality Scheduling

“…MC scheduling with scaled deadlines Deadline-scaling for mixed-criticality systems originates with EDF-VD ("Earliest Deadline First -with Virtual Deadlines") [5]. EDF-VD uses standard EDF scheduling rules but, instead of reporting the real deadlines to the EDF scheduler for scheduling decisions, it reports shorter deadlines (if needed) for H-tasks during L-mode operation.…”

“…NPS-F is server-based, which helps provide both fairness to low-criticality tasks and strict temporal isolation between high-and low-criticality tasks. The new algorithm employs the per-task deadline scaling scheduling technique by Ekberg and Yi [4], an extension of EDF-VD [5]. NPS-F-MC allows migration among processors only for servers for low-criticality tasks, with less severe safety considerations.…”