《操作系统导论》第九章 调度:比例份额 课后习题

本章又介绍了不同于前面章节的两种调度算法：彩票调度、步长调度(用于解决彩票调度不确性的问题)

本章作业需要下载书中提到的 lottery.py 文件，请移HomeWork

限于篇幅，只粘贴出了源程序的核心部分

理解源程序：

输入参数

parser.add_option('-s', '--seed', default=0, help='the random seed',              action='store', type='int', dest='seed')
parser.add_option('-j', '--jobs', default=3, help='number of jobs in the system', action='store', type='int', dest='jobs')
parser.add_option('-l', '--jlist', default='', help='instead of random jobs, provide a comma-separated list of run times and ticket values (e.g., 10:100,20:100 would have two jobs with run-times of 10 and 20, each with 100 tickets)',  action='store', type='string', dest='jlist')
parser.add_option('-m', '--maxlen',  default=10,  help='max length of job',         action='store', type='int', dest='maxlen')
parser.add_option('-T', '--maxticket', default=100, help='maximum ticket value, if randomly assigned',          action='store', type='int', dest='maxticket')
parser.add_option('-q', '--quantum', default=1,   help='length of time slice', action='store', type='int', dest='quantum')
parser.add_option('-c', '--compute', help='compute answers for me', action='store_true', default=False, dest='solve')

• -s 是用于指定产生随机数的种子，默认为 0
• -j 指定任务的数量，默认为 3
• -l 代表一个任务列表（任务的运行时间:任务携带的票数），默认为空
• -m 指定任务的最大长度，默认为 10
• -T 指定每个任务最大携带的彩票数量，默认为 100
• -q 时间片的长度，默认为 1
• -c 指定是否计算彩票调度模拟解，默认为False

产生随机彩票数

r = int(random.random() * 1000001)
        winner = int(r % tickTotal)

调度模拟

        for (job, runtime, tickets) in joblist:
            current += tickets
            if current > winner:
                (wjob, wrun, wtix) = (job, runtime, tickets)
                break

遍历任务列表，查找当前随机数产生的彩票数量位于哪个区间，进而决定调度哪个任务执行

第一题

1．计算3个工作在随机种子为1、2和3时的模拟解。

执行 lottery.py -j 3 -s 1 -c True

>lottery.py -j 3 -s 1 -c True
ARG jlist
ARG jobs 3
ARG maxlen 10
ARG maxticket 100
ARG quantum 1
ARG seed 1

Here is the job list, with the run time of each job:
  Job 0 ( length = 1, tickets = 84 )
  Job 1 ( length = 7, tickets = 25 )
  Job 2 ( length = 4, tickets = 44 )


** Solutions **

Random 651593 -> Winning ticket 119 (of 153) -> Run 2
  Jobs:
 (  job:0 timeleft:1 tix:84 )
 (  job:1 timeleft:7 tix:25 )
 (* job:2 timeleft:4 tix:44 )

Random 788724 -> Winning ticket 9 (of 153) -> Run 0
  Jobs:
 (* job:0 timeleft:1 tix:84 )
 (  job:1 timeleft:7 tix:25 )
 (  job:2 timeleft:3 tix:44 )

--> JOB 0 DONE at time 2
Random 93859 -> Winning ticket 19 (of 69) -> Run 1
  Jobs:
 (  job:0 timeleft:0 tix:--- )
 (* job:1 timeleft:7 tix:25 )
 (  job:2 timeleft:3 tix:44 )

Random 28347 -> Winning ticket 57 (of 69) -> Run 2
  Jobs:
 (  job:0 timeleft:0 tix:--- )
 (  job:1 timeleft:6 tix:25 )
 (* job:2 timeleft:3 tix:44 )

Random 835765 -> Winning ticket 37 (of 69) -> Run 2
  Jobs:
 (  job:0 timeleft:0 tix:--- )
 (  job:1 timeleft:6 tix:25 )
 (* job:2 timeleft:2 tix:44 )

Random 432767 -> Winning ticket 68 (of 69) -> Run 2
  Jobs:
 (  job:0 timeleft:0 tix:--- )
 (  job:1 timeleft:6 tix:25 )
 (* job:2 timeleft:1 tix:44 )

--> JOB 2 DONE at time 6
Random 762280 -> Winning ticket 5 (of 25) -> Run 1
  Jobs:
 (  job:0 timeleft:0 tix:--- )
 (* job:1 timeleft:6 tix:25 )
 (  job:2 timeleft:0 tix:---