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^b. We also compare the schedulability of Sr^b to other pinwheel schedulers Sx, Sr, and Sx^b. Although EDF has the biggest schedulable task set than RM and Sr^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^b schedules the tasks according to a set of transformed harmonic distance constraints, the produced schedule is very regular and provides the best predictability.