Periodic and aperiodic task scheduling in strongly partitioned integrated real-time systems

To facilitate the integration of real-time applications in a common platform, temporal and spatial partitioning should be provided. A strongly partitioned integrated real-time system (SPIRIT) is reported in this paper that adopts a two-level hierarchical scheduling mechanism to ensure temporal partitioning. At the lower level, multiple partitions (applications) are dispatched under a cyclic scheduling, whereas, at the higher level, multiple periodic tasks of a partition are scheduled within the partition according to a fixed priority algorithm. The proposed Distance Constraint guaranteed Dynamic Cyclic (DC²) scheduler applies three basic operations, left-sliding, right-putting and compacting, to dynamically schedule aperiodic tasks and, in the meantime, guarantees 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 simulation studies, we observe that the DC² algorithm 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.