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 renting overhead. However static scheduling handles non-periodic processing inefficiently, and treats invocation-to-invocation variations in resource requirements inflexibly. As a consequence, processing resources am underutilized and the resulting systems are hard to adapt to meet worst-case processing requirements. Dynamic scheduling has the potential to offer relief from some of the restrictions imposed by strict static scheduling approaches. Potential benefits of dynamic scheduling include better tolerance for variations in activities, more flexible prioritization, and better CPU utilization in the presence of non-periodic activities. However the cost of these benefits is expected to be higher run-time scheduling overhead and additional application development complexity. This report reviews the implications of these tradeoffs for avionics mission computing systems and presents experimental results obtained using the Maximum Urgency First dynamic scheduling algorithm.