可支持多级关键度任务的实时操作系统

为设计可支持多级关键度任务的军用实时操作系统MRTOS,首先分析了现有实时操作系统的调度机制。同时为定量描述任务的关键度,使用时间窗口来描述任务在有限时间范围内的时限错过情况。基于此描述,提出了改进型的最短紧急距离优先调度算法,该算法可保证实时任务仅错过规定数量的时限,能有效支持不同关键度任务同时运行在同一计算机上,同时可在任务量瞬时过载的情况下保证关键任务优先得到执行。最后通过仿真对最短紧急距离优先调度算法进行了例证。

Real-time operating system supporting tasks of multilevel criticality

To design the safety-critical real-time operating system,named military RTOS(MRTOS),which can support mixed criticality real-time tasks,the status of the existing scheduling mechanisms of real-time operating systems is firstly analyzed.A window-constraint technique is adopted to investigate the violation of task's deadline over a finite time range while task is consecutively invocated,which is used to define the criticality of real-time task.As a result,a real-time scheduling algorithm based on improved shortest urgent distance first(ESUDF) is proposed,The algorithm guarantees a real-time task to just miss the specified deadline.Therefore,ESUDF can efficiently support the mixed criticality tasks to run on the same computer.At the same time,the high criticality real-time task is preferentially executed in case of instantaneous overload of tasks.At last,ESUDF algorithm is exemplified via simulation.