提出一种混合的任务调度方法:当任务集不能整体满足严格周期条件时,选择部分重要的或易于调度的任务进行严格周期调度,其他周期任务基于最小抖动准则调度,也就是使任务相邻作业之间间隔的差值尽可能小。针对这种混合调度方法,给出了严格周期可调度性评价方案,考虑了不同长度作业占据时隙的可行情况,并利用min-plus代数的概念进行转移权重矩阵的乘法运算,用以寻找当前任务的最小抖动时隙分配方案。研究表明,与仅采用最小抖动准则分配的对照组相比,混合调度方法提高了严格周期任务的比例,并且得到的调度方案在最坏情况下抖动率更小。
A hybrid task scheduling method is presented, in which strict periodicity criteria is adopted to certain important or easy-to-schedule tasks, while the rest is scheduled based on the jitter minimization criteria to mitigate the variance of intervals between any two adjacent jobs of a given task. To develop this method, a measure for strict periodicity sehedulability, and a feasible slot selection scheme for variable-length jobs are proposed. The rain-plus algebra is used for making multiplication of weighted transferring matrix, thus to implement slot allocation with minimum jitter of current task. Case study shows that : Compared with the control groups only based on minimum jitter scheduling, our hybrid method can gain increased proportion of strictly periodic tasks and the scheduling scheme obtained has smaller jitter rate in the worst case.