On the schedulability conditions on partial time slots

A real-time round robin, which is a novel real-time scheduling algorithm, is proposed in this paper. It is a time slot-based algorithm. Tasks are divided into groups and each group of tasks is statically assigned a subset of time slots. In a group, tasks are scheduled by earliest deadline first (EDF). We introduce "regular" subsets of time slots. This has the advantage that any periodic tasks can be scheduled only at time slots contained in the subset using the minimum number of time slots. We show a method to divide the universal set of time slots into at least two regular subsets. Consequently, the real-time round robin algorithm can schedule periodic tasks whose processor utilization factor does not exceed 100% at a lower scheduling cost than that of the EDF algorithm. Moreover, no missed deadline of a task in one group affect the tasks in any other groups.