随机弱实时系统作业调度概率保证分析

随机弱实时系统与强实时系统的显著区别是 ,它不要求实时任务的每一项作业都满足时限要求 ,只要保证作业的时限延误率低于某一阈值 ,其总体执行性能就是可以接受的。提出了概率时间需求分析法 (PTDA) ,用于估计可剥夺静态优先级调度策略下周期性任务的作业满足时限约束的概率的下界 ,并通过一个具体的实例考察了下界的紧性。对实例系统的仿真结果表明 ,PTDA分析的误差小于 1 0 % ,计算速度快 ,可以为弱实时应用的设计提供重要的参考依据

Probabilistic Scheduling Guarantee Analysis for Jobs in Stochastic Soft Real-Time Systems

Stochastic soft real time systems distinguish themselves from hard real time systems in that there is no demand for every job in a task to meet its deadline.For these systems,provided that job deadline missing rate is below some threshold,total performance is acceptable. For a fixed priority preemptive scheduled soft real time system, we present probabilistic time demand analysis technique by which a lower bound on the probability that a job in a periodic task meets its deadline is estimated . We have also performed a simulation study of an example system and check the tightness of the lower bound.The simulation results shows PTDA has a high speed and an error below 10%. It can provide important reference for the design of soft real time application.