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首页> 外文学位 >Equitable shortest job first: A preemptive scheduling algorithm for soft real-time systems.
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Equitable shortest job first: A preemptive scheduling algorithm for soft real-time systems.

机译：公平最短的作业优先：用于软实时系统的抢先式调度算法。

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摘要

The Shortest Job First algorithm gives the optimal average turnaround time for a set of processes, but it suffers from starvation for long processes. Starvation occurs when a long process is denied processor resources because the resources are occupied by short processes, thus, causing the long process to potentially never finish its task. This thesis considers that the short processes are soft real time processes. It presents the designer with a choice to select an algorithm that provides close to optimal average turnaround time within the soft deadline for short processes as compared to the Shortest Job First algorithm which results in decreased average turnaround time for long processes. The proposed algorithm improves drawback, related to long job starvation, in Preemptive-Shortest Job First by providing protection to a process through prioritization. A priority is assigned to a process based on a percentage of its burst time to completion, by introducing the parameter Theta, or the time spent by the process in the waiting queue, by introducing the parameter Lambda. Theta protects a current running process from being preempted when its execution time reaches a percentage of its total computing time. Lambda gives priority to a process when it exceeds a certain amount of time in the waiting queue. Four variants of the proposed scheduling methodology, each using a different theta and lambda, have been developed.;The performances of these variants are compared against Highest Response Ratio Next (HRRN), Railroad, Enhanced Shortest Job First (ESJF), and Alpha scheduling algorithms that have been previously proposed. Experimental results show that our proposed algorithm performs better in terms of reducing the average turnaround time of the long processes while maintaining the turnaround time on the short processes at low desired levels, as those required for soft real time tasks.
机译：最短作业优先算法为一组进程提供了最佳的平均周转时间，但对于长进程却很饿。当长进程由于短进程占用了资源而拒绝了长进程时，就会发生饥饿，因此，长进程可能永远无法完成其任务。本文认为短过程是软实时过程。与最短作业优先算法相比，它为设计人员提供了一个选择，可以选择一种算法，该算法可以在软期限内为短流程提供接近最佳的平均周转时间，而这可以减少长流程的平均周转时间。所提出的算法通过为优先级提供对进程的保护，从而改善了先占式最短作业优先级中与长期饥饿相关的缺点。通过引入参数Theta，基于进程完成时间的百分比为进程分配优先级，或者通过引入参数Lambda，将优先级分配给进程，或者将进程在等待队列中花费的时间分配给进程。当执行时间达到其总计算时间的百分比时，Theta可以防止当前正在运行的进程被抢占。当Lambda在等待队列中超过一定时间时，它将优先处理该进程。已开发出建议的调度方法的四个变体，每个变体使用不同的theta和lambda .;将这些变体的性能与最高响应率下一个（HRRN），铁路，增强型最短作业优先（ESJF）和Alpha调度进行了比较先前已经提出的算法。实验结果表明，我们提出的算法在减少长流程的平均周转时间的同时，将短流程的周转时间保持在较低的期望水平上表现出更好的性能，这是软实时任务所需的。

著录项

  • 作者

    Rene, Mario Jean.;

  • 作者单位

    Southern Illinois University at Carbondale.;

  • 授予单位 Southern Illinois University at Carbondale.;
  • 学科 Engineering Computer.;Computer Science.
  • 学位 M.S.
  • 年度 2014
  • 页码 71 p.
  • 总页数 71
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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