可支持多级关键度任务的实时操作系统

Real-time operating system supporting tasks of multilevel criticality

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。

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.