RM算法中减少抢占开销的任务微调算法

在基于嵌入式实时操作系统的实时应用中,由于任务抢占导致的切换开销对于整个系统是不可忽略的.提出了一种减少抢占发生的RM任务微调算法,通过对固定优先级调度抢占行为可推迟时间的量化分析,推导出受低优先级任务阻塞而造成的受阻任务集,以及在任意抢占时刻,推迟高优先级实时任务执行避免抢占发生的判定条件.仿真实验表明该算法在保证可调度任务集中所有任务满足时限约束的前提下,延迟高优先级任务的执行,减少抢占发生次数,通过减少抢占开销提高RM算法在实际应用中的可调度利用率.

A Task Fine-Tuning Algorithm to Reduce Preemption Overhead of RM Algorithm

In embedded real-time applications based on embedded real-time operating systems,the task context switch overhead incurred by preemptions cannot be ignored compared with the overall system.To solve the problem,a preemption reduction algorithm is presented to reduce the occurrence of preemption.While quantitatively analyzing suspension time of fixed priority scheduling preemption actions,the blocked task set obstructed by low priority tasks and the determinant condition was deduced to avoid preemption in the arbitrary preemption moment by postponing high-priority tasks in hard real-time systems.Simulation results showed that the optimization strategy presented effectively reduced the number of task preemptions and the preemption overhead,while ensuring task scheduling.The algorithm postpones the running of high-priority tasks to avoid occurrence of unnecessary preemptions and guarantees that each task in the schedulable task set meets its deadline.Thus,the algorithm improves practical schedulable utilization of the RM algorithm by reducing preemption overhead in practical applications.