针对弱硬实时系统的DRM调度算法

本文在定义支持多级QoS的弱硬实时系统周期任务模型的基础上,提出基于RM调度策略的弱硬实时调度算法DRM,它具备可调度判定不等式,不限定任务的QoS参数模式,并通过在调度的过程中动态调整任务的优先级来反映其紧迫程度.在系统过载时,DRM调度算法可以采用QoS退化机制,在保证紧要任务以及其所要求的最低QoS执行的同时,适当降低某些任务的服务等级,使得更多的任务可以有效运行,以此来提高系统对负载的适应性.最后,本文通过仿真实验,验证了DRM以及QoS退化机制的有效性.

DRM Scheduling Algorithm for Weakly Hard Real-Time System

After defining the model of periodic task with multiple QoS grades for weakly hard real-time system, this paper presents DRM weakly hard real-time scheduling algorithm based on RM scheduling policy. DRM, Which has inequation for schedulablity test, not only supports task with any QoS parameter, but also changes the scheduling priority of task during scheduling to reflect its pressure. When system is overloaded,DRM can adopt QoS degradation mechanism, which enhances the flexibility of system to load by reducing service grade of tasks properly with the guarantee of important tasks scheduling with lowest QoS, so as to make more tasks running validly. At the end of this paper, simulated data is presented to show the efficiency of DRM and QoS degradation mechanism.