DC/sup 2/ scheduling for aperiodic tasks in strongly partitioned real-time systems

The strongly partitioned real time system (SP-RTS) provides temporal and spatial partitioning for its integrated real time applications. The SP-RTS architecture adopts a two-level hierarchical scheduling mechanism. In the lower level, multiple partitions (applications) are dispatched under a cyclic scheduling, whereas, in the higher level, multiple periodic tasks of each partition are scheduled according to a fixed priority algorithm. The authors focus on designing algorithms for online scheduling of aperiodic tasks in the SP-RTS environment. The Distance Constraint guaranteed Dynamic Cyclic (DC/sup 2/) scheduler that is proposed uses these basic operations: Left Sliding (LS), Right Putting (RP), and Compacting. These operations dynamically schedule aperiodic tasks within a distance-constrained cyclic schedule. We show that the dynamic applications of these operations do not violate the distance constraint characteristics of a partition cyclic schedule. In addition, the slack time calculation of these dynamic operations can be applied for scheduling hard aperiodic tasks. With the simulation studies, we observed that the DC/sup 2/ can result in a significant performance enhancement in terms of the average response time of soft aperiodic tasks and the acceptance rate for hard aperiodic tasks.