关键词: 嵌入式实时系统, 实时调度算法, 反馈控制, 处理器利用率, 任务错过率

Abstract:

In order to solve the problem that embedded real-time systems' miss rate of real-time task is too high and the problem of poor stability of real-time scheduling while the load of the system is uncertain, a scheduling model based on feedback control was proposed. This model consisted of an improved multi-level queue scheduler and three controllers, those were access controller, execution level controller and Proportional-Integral-Derivative (PID) controller. The deviation of task miss rate was feedbacked to the PID controller and generated a corresponding adjustment, the adjustment acted on the other two controllers to adjust the level of real-time tasks. Tasks adjusted were executed by the scheduler. After structural adjustment and improvement, the scheduling model was applied in embedded Configurable operating system (eCos). The experimental results show that the proposed method can reduce miss rate of tasks, and solve the overload problem of the system.

Key words: embedded real-time system, real-time scheduling algorithm, feedback control, processor utilization, task miss rate