ostep homework(7)

本文最后更新于：1 年前

第7章 进程调度：介绍 homework详解

实验环境

笔者采用的是Ubuntu22.04的虚拟机。
本次作业需要先通过所学知识手动解题，再按教程运行程序scheduler.py即可。
需要用到cpu-sched文件，先阅读readme文件。

实验内容

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$ ./scheduler.py -p SJF -l 200,200,200 -c
ARG policy SJF
ARG jlist 200,200,200

Here is the job list, with the run time of each job: 
  Job 0 ( length = 200.0 )
  Job 1 ( length = 200.0 )
  Job 2 ( length = 200.0 )


** Solutions **

Execution trace:
  [ time   0 ] Run job 0 for 200.00 secs ( DONE at 200.00 )
  [ time 200 ] Run job 1 for 200.00 secs ( DONE at 400.00 )
  [ time 400 ] Run job 2 for 200.00 secs ( DONE at 600.00 )

Final statistics:
  Job   0 -- Response: 0.00  Turnaround 200.00  Wait 0.00
  Job   1 -- Response: 200.00  Turnaround 400.00  Wait 200.00
  Job   2 -- Response: 400.00  Turnaround 600.00  Wait 400.00

  Average -- Response: 200.00  Turnaround 400.00  Wait 200.00
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$ ./scheduler.py -p FIFO -l 200,200,200 -c
ARG policy FIFO
ARG jlist 200,200,200

Here is the job list, with the run time of each job: 
  Job 0 ( length = 200.0 )
  Job 1 ( length = 200.0 )
  Job 2 ( length = 200.0 )


** Solutions **

Execution trace:
  [ time   0 ] Run job 0 for 200.00 secs ( DONE at 200.00 )
  [ time 200 ] Run job 1 for 200.00 secs ( DONE at 400.00 )
  [ time 400 ] Run job 2 for 200.00 secs ( DONE at 600.00 )

Final statistics:
  Job   0 -- Response: 0.00  Turnaround 200.00  Wait 0.00
  Job   1 -- Response: 200.00  Turnaround 400.00  Wait 200.00
  Job   2 -- Response: 400.00  Turnaround 600.00  Wait 400.00

  Average -- Response: 200.00  Turnaround 400.00  Wait 200.00

这两个代码块分别是SJF和FIFO调度，因为三个任务长度相等且同时到达，所以它们的响应时间和周转时间相同。

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$ ./scheduler.py -p SJF -l 100,200,300 -c
ARG policy SJF
ARG jlist 100,200,300

Here is the job list, with the run time of each job: 
  Job 0 ( length = 100.0 )
  Job 1 ( length = 200.0 )
  Job 2 ( length = 300.0 )


** Solutions **

Execution trace:
  [ time   0 ] Run job 0 for 100.00 secs ( DONE at 100.00 )
  [ time 100 ] Run job 1 for 200.00 secs ( DONE at 300.00 )
  [ time 300 ] Run job 2 for 300.00 secs ( DONE at 600.00 )

Final statistics:
  Job   0 -- Response: 0.00  Turnaround 100.00  Wait 0.00
  Job   1 -- Response: 100.00  Turnaround 300.00  Wait 100.00
  Job   2 -- Response: 300.00  Turnaround 600.00  Wait 300.00

  Average -- Response: 133.33  Turnaround 333.33  Wait 133.33
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$ ./scheduler.py -p FIFO -l 100,200,300 -c
ARG policy FIFO
ARG jlist 100,200,300

Here is the job list, with the run time of each job: 
  Job 0 ( length = 100.0 )
  Job 1 ( length = 200.0 )
  Job 2 ( length = 300.0 )


** Solutions **

Execution trace:
  [ time   0 ] Run job 0 for 100.00 secs ( DONE at 100.00 )
  [ time 100 ] Run job 1 for 200.00 secs ( DONE at 300.00 )
  [ time 300 ] Run job 2 for 300.00 secs ( DONE at 600.00 )

Final statistics:
  Job   0 -- Response: 0.00  Turnaround 100.00  Wait 0.00
  Job   1 -- Response: 100.00  Turnaround 300.00  Wait 100.00
  Job   2 -- Response: 300.00  Turnaround 600.00  Wait 300.00

  Average -- Response: 133.33  Turnaround 333.33  Wait 133.33

因为是按照100，200，300的顺序插入任务的，所以二者调度模式是相同的，如果将100，200，300的顺序交换，结果会产生差异。例如，

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$ ./scheduler.py -p FIFO -l 200,100,300 -c
ARG policy FIFO
ARG jlist 200,100,300

Here is the job list, with the run time of each job: 
  Job 0 ( length = 200.0 )
  Job 1 ( length = 100.0 )
  Job 2 ( length = 300.0 )


** Solutions **

Execution trace:
  [ time   0 ] Run job 0 for 200.00 secs ( DONE at 200.00 )
  [ time 200 ] Run job 1 for 100.00 secs ( DONE at 300.00 )
  [ time 300 ] Run job 2 for 300.00 secs ( DONE at 600.00 )

Final statistics:
  Job   0 -- Response: 0.00  Turnaround 200.00  Wait 0.00
  Job   1 -- Response: 200.00  Turnaround 300.00  Wait 200.00
  Job   2 -- Response: 300.00  Turnaround 600.00  Wait 300.00

  Average -- Response: 166.67  Turnaround 366.67  Wait 166.67

响应时间和周转时间都发生了变化。

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$ ./scheduler.py -p RR -l 100,200,300 -c
ARG policy RR
ARG jlist 100,200,300

Here is the job list, with the run time of each job: 
  Job 0 ( length = 100.0 )
  Job 1 ( length = 200.0 )
  Job 2 ( length = 300.0 )


** Solutions **

Execution trace:
  [ time   0 ] Run job   0 for 1.00 secs
  [ time   1 ] Run job   1 for 1.00 secs
  [ time   2 ] Run job   2 for 1.00 secs
  [ time   3 ] Run job   0 for 1.00 secs
  [ time   4 ] Run job   1 for 1.00 secs
  ……
  [ time 598 ] Run job   2 for 1.00 secs
  [ time 599 ] Run job   2 for 1.00 secs ( DONE at 600.00 )

Final statistics:
  Job   0 -- Response: 0.00  Turnaround 298.00  Wait 198.00
  Job   1 -- Response: 1.00  Turnaround 499.00  Wait 299.00
  Job   2 -- Response: 2.00  Turnaround 600.00  Wait 300.00

  Average -- Response: 1.00  Turnaround 465.67  Wait 265.67

采用RR调度程序交换三者顺序也不会有影响了，牺牲了周转时间和等待时间换取了极快的响应时间。

4

当工作负载为长度自小到大升序排列时，二者产生的效果是一样的，其周转时间和等待时间一致。

5

当量子长度大于最大工作负载长度时，二者等效。

6

容易得出结论，工作负载长度增加，其必然会使响应时间增加。

7

量子长度增加，响应时间会随之增加。
当给定N个任务时，假设量子长度为m

  1. 当每个任务长度都大于m时，其响应时间为

    ∑i=1Ni×mN=m(N+1)2{\sum_{i=1}^N i\times m\over N}={m(N+1)\over2}

  2. 当每个任务长度都小于m时，其响应时间为总任务长度除以N。

操作系统 ostep homework详解

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