Dynamic Scheduling Strategies for Avionics Mission Computing

Avionics mission computing systems have traditionally been scheduled statically. Static scheduling provides assurance of schedulability prior to run-time and can be implemented with low run-time overhead. However, static scheduling does not support distributed processing effectively, handles non-periodic processing inefficiently, and treats invocation-toinvocation variations in resource requirements inflexibly. As a consequence, processing resources are underutilized and the resulting systems are hard to adapt to meet real-time processing requirements. Dynamic scheduling offers relief from the limitations of static scheduling. However, dynamic scheduling often has a higher run-time cost because certain operations are performed on-line. In addition, tasks can be scheduled dynamically that may never be dispatched. This report reviews the implications of these factors on avionics mission computing systems. We present an approach to dynamic scheduling, based on the Maximum Urgency First al..