Dynamic scheduling of skippable periodic tasks in weakly-hard real-time systems

This paper deals with dynamic scheduling in real-time systems that have Quality of Service requirements. We assume that tasks are periodic and may miss their deadlines, occasionally, as defined by the so-called Skip-Over model. In this paper, we present a dynamic scheduling algorithm, called RLP (Red as Late as possible), a variant of Earliest Deadline to make slack stealing and get better performance in terms of ratio of periodic task instances which complete before their deadline. Simulation results show that RLP outperforms the two conventional skip-over algorithms, namely RTO (Red Tasks Only) and BWP (Blue When Possible), introduced about ten years ago. Finally, we present the integration of these QoS scheduling services into CLEOPATRE(1) a free open-source library which offers selectable real-timefacilities on shelves.