Minimizing the overhead of dynamic scheduling strategies in avionics systems

There are two main types of process scheduling strategies which can be used in aircraft/spacecraft avionics systems. In static strategies, priorities are statically assigned to processes prior to run time. These strategies have two main disadvantages. First,they are not applicable to systems in which there is not enough information available about run time requirements of processes in advance. Second, they limit CPU utilization. In fact, these strategies waste some CPU cycles because they have to provide for the critical instant of each process. In dynamic strategies, priorities are dynamically assigned to processes based on laxities or other run time parameters. These strategies theoretically do not restrict CPU utilization but they produce some run time overhead which is mainly related to the time required to sort processes in the ready queue each time a process is preempted. This paper proposes and evaluates a novel approach to minimizing the time consumed by the sorting algorithm. This approach is based on the mathematical properties of laxities (or other dynamic priority variables). It can be shown that the approach mentioned above can reduce the time complexity of the sorting algorithm, in terms of the number of processes (n), from O(nlogn) to O(n). This can considerably improve the performance of the aircraft/spacecraft avionics system.