Schedulability comparisons among periodic and distance-constrained real-time schedulers

Tasks in a real-time system must be scheduled to meet their timing constraints. In this paper, we discuss the schedulability relationship among two well-known schedulers EDF and RM, and a recently proposed scheduler Sr/sup b/. We also compare the schedulability of Sr/sup b/ to other pinwheel schedulers Sx, Sr, and Sx/sup b/. Although EDF has the biggest schedulable task set than RM and Sr/sup b/, the schedules produced by EDF are the most vulnerable to system overloads and with the least predictability. RM has a better predictability than EDF for tasks with a high priority but not for lower priority tasks. Since Sr/sup b/ schedules the tasks according to a set of transformed harmonic distance constraints, the produced schedule is very regular and provides the best predictability.