一种新型实时调度算法研究

Study on a New Kind of Real-Time Scheduling Algorithm

在许多片上特定应用系统中,任务多且切换频繁,任务切换开销大,有时甚至严重影响系统的可调度性.研究了动态可抢占门限调度算法,它通过初始门限值、动态门限值的计算和优化线程分配,实现了在处理器高利用率下,有效降低任务切换开销的目的,并相应地减少了对内存的需求.动态可抢占门限调度算法是将静态抢占门限算法与动态调度算法有机地结合在一起,完成了由静态到动态无缝转换.

Many application specific operating systems based on system on chip are composed of lots of tasks that can generate multi-tasking under preemptive scheduling. Preemptive multi-tasking incurs high preemption switching overheads, and these costs may jeopardize a system schedulability. A novel scheduling, named dynamic preemption threshold, is proposed here. The scheduling can reduce preemption costs by thread assignment and changing task dynamic preemption threshold at run time. Because dynamic preemption threshold is based on dynamic algorithm, it can achieve a high processor utilization with relative low cost in context switching and memory requirement. The scheduling perfectly integrates preemption threshold scheduling into EDF algorithm, and accomplishes to transform static model to dynamic algorithm seamlessly.