Exact speedup factors and sub-optimality for non-preemptive scheduling
Exact speedup factors and sub-optimality for non-preemptive scheduling
复制标题
非抢占式调度的精确加速因子和次优性
作者：
Robert I. Davis;Abhilash Thekkilakattil;Oliver Gettings;R. Dobrin;S. Punnekkat;Jian
固定优先级调度在许多实时系统中使用；然而，与最优单处理器调度算法（如抢占式最早截止日期优先（EDF-P））相比，已知抢占式和非抢占式变体（FP-P和FP-NP）都是次优的。本文研究了固定优先级非抢占调度的次优性问题。具体地说，我们推导了保证任何任务集在FP-NP下可行（即假设最优优先级分配的可调度性）所需的精确处理器加速因子。作为这项工作的结果，我们还导出了非抢占式EDF （EDF- np）次最优性的下界。由于这个下界与最近公布的相同数量的上界相匹配，因此它关闭了EDF-NP的精确次最优性。我们知道，抢占式固定优先级调度和非抢占式固定优先级调度都不占优势，换句话说，在FP-P下单位速度处理器上可行的任务集在FP-NP下不可行的任务集，反之亦然。因此，比较这两种算法，在两个方向上都有非平凡的加速因子。我们导出了保证任意FP-P可行任务集FP-NP可行性所需的精确加速因子。进一步，我们导出了保证任何有约束期限的FP-NP可行任务集FP-P可行性所需的精确加速因子。
Fixed priority scheduling is used in many real-time systems; however, both preemptive and non-preemptive variants (FP-P and FP-NP) are known to be sub-optimal when compared to an optimal uniprocessor scheduling algorithm such as preemptive earliest deadline first (EDF-P). In this paper, we investigate the sub-optimality of fixed priority non-preemptive scheduling. Specifically, we derive the exact processor speed-up factor required to guarantee the feasibility under FP-NP (i.e. schedulability assuming an optimal priority assignment) of any task set that is feasible under EDF-P. As a consequence of this work, we also derive a lower bound on the sub-optimality of non-preemptive EDF (EDF-NP). As this lower bound matches a recently published upper bound for the same quantity, it closes the exact sub-optimality for EDF-NP. It is known that neither preemptive, nor non-preemptive fixed priority scheduling dominates the other, in other words, there are task sets that are feasible on a processor of unit speed under FP-P that are not feasible under FP-NP and vice-versa. Hence comparing these two algorithms, there are non-trivial speedup factors in both directions. We derive the exact speed-up factor required to guarantee the FP-NP feasibility of any FP-P feasible task set. Further, we derive the exact speed-up factor required to guarantee FP-P feasibility of any constrained-deadline FP-NP feasible task set.
影响因子：
1.3
作者：
S. Altmeyer;Robert I. Davis;Claire Maiza
通讯作者：
S. Altmeyer;Robert I. Davis;Claire Maiza
基于抢占式和非抢占式范例的加速因子的固定优先级和 EDF 调度的精确比较
影响因子：
1.3
作者：
Davis R
通讯作者：
Davis R