基于动态抢占阈值的实时调度

具有抢占阈值的调度算法集非抢占调度和纯抢占调度的特点，既减少了由于过多的随意抢占造成的CPU资源浪费，又保证了一定的任务截止期错失率及CPU资源利用率。已有的工作基本集中于讨论任务集完全给定，任务数、任务的优先级及任务的抢占阈值在调度前已完全确定，而且要求不同的任务具有不同的优先级，提出的具有抢占阈值的调度算法，完全放松了对这些条件的限制，即任务的个数不确定，任务的优先级及其抢占阈值在调度过程中可以动态地变化。最后以常用的LSF调度策略为例，结合动态的抢占阈值进行仿真，仿真结果表明，对于不确定的任务集、任务优先级和抢占阈值，利用具有抢占阈值的动态调度算法，降低了任务截止期错失率、提高了CPU的有效使用率。

Scheduling Dynamic Real-Time Tasks with Preemption Threshold

Scheduling algorithms with preemption threshold collect characteristics of no preemption scheduling and full preemption scheduling It both decreases the waste of CPU resources caused by excessive random preemptions and guarantees suitable missed deadline percentage and CPU utilization However, the existing works basically focus on a determinated task set (i e , a given number of tasks, fixed priority and a given preemption threshold satisfied a certain condition), and require that different task has a different priority integer The proposed scheduling algorithm with preemption threshold discussed in this paper relaxes the above limitations, i e , an uncertain number of tasks, and the priority and its preemption threshold can be dynamically changed during scheduling Finally, using usual LSF policy as example, simulations with dynamic preemption threshold are given Results show that the proposed dynamic scheduling algorithm with preemption threshold decreases the missed deadline percentage and increases efficient utilization percentage of CPU greatly for uncertain task set with no fixed priority and preemption threshold