第4章 抽象：进程 homework详解
写在前面
开个新坑，csapp读到汇编看不下去了，故转战操作系统。
题目在书中有提到，这里不再重复赘述（懒）。
实验材料从官网下载就好，贴个传送门。
建议在实验开始之前仔细阅读 readme 文件。
实验环境
笔者采用的是Ubuntu22.04的虚拟机。
本次作业用到 cpu-intro 文件
实验内容
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| $ ./process-run.py -l 5:100,5:100 -c -p
Time PID: 0 PID: 1 CPU IOs
1 RUN:cpu READY 1
2 RUN:cpu READY 1
3 RUN:cpu READY 1
4 RUN:cpu READY 1
5 RUN:cpu READY 1
6 DONE RUN:cpu 1
7 DONE RUN:cpu 1
8 DONE RUN:cpu 1
9 DONE RUN:cpu 1
10 DONE RUN:cpu 1
Stats: Total Time 10
Stats: CPU Busy 10 (100.00%)
Stats: IO Busy 0 (0.00%)
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运行完第一个进程紧接着运行第二个进程，cpu利用率100%。
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| $ ./process-run.py -l 4:100,1:0 -c -p
Time PID: 0 PID: 1 CPU IOs
1 RUN:cpu READY 1
2 RUN:cpu READY 1
3 RUN:cpu READY 1
4 RUN:cpu READY 1
5 DONE RUN:io 1
6 DONE WAITING 1
7 DONE WAITING 1
8 DONE WAITING 1
9 DONE WAITING 1
10 DONE WAITING 1
11* DONE RUN:io_done 1
Stats: Total Time 11
Stats: CPU Busy 6 (54.55%)
Stats: IO Busy 5 (45.45%)
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这里先运行第一个进程时会阻塞第二个进程运行，所以要依此进行。
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| $ ./process-run.py -l 1:0,4:100 -c -p
Time PID: 0 PID: 1 CPU IOs
1 RUN:io READY 1
2 WAITING RUN:cpu 1 1
3 WAITING RUN:cpu 1 1
4 WAITING RUN:cpu 1 1
5 WAITING RUN:cpu 1 1
6 WAITING DONE 1
7* RUN:io_done DONE 1
Stats: Total Time 7
Stats: CPU Busy 6 (85.71%)
Stats: IO Busy 5 (71.43%)
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容易发现交换顺序是会对运行时间和效率产生影响的，运行io时可以同时运行cpu。
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| $ ./process-run.py -l 1:0,4:100 -c -S SWITCH_ON_END -p
Time PID: 0 PID: 1 CPU IOs
1 RUN:io READY 1
2 WAITING READY 1
3 WAITING READY 1
4 WAITING READY 1
5 WAITING READY 1
6 WAITING READY 1
7* RUN:io_done READY 1
8 DONE RUN:cpu 1
9 DONE RUN:cpu 1
10 DONE RUN:cpu 1
11 DONE RUN:cpu 1
Stats: Total Time 11
Stats: CPU Busy 6 (54.55%)
Stats: IO Busy 5 (45.45%)
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如果限制了当进行io操作时，系统不允许切换到另一个进程，则产生的效果和不交换顺序时相同。
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| $ ./process-run.py -l 1:0,4:100 -c -S SWITCH_ON_IO -p
Time PID: 0 PID: 1 CPU IOs
1 RUN:io READY 1
2 WAITING RUN:cpu 1 1
3 WAITING RUN:cpu 1 1
4 WAITING RUN:cpu 1 1
5 WAITING RUN:cpu 1 1
6 WAITING DONE 1
7* RUN:io_done DONE 1
Stats: Total Time 7
Stats: CPU Busy 6 (85.71%)
Stats: IO Busy 5 (71.43%)
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和3一致，不做解释。
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| $ ./process-run.py -l 3:0,5:100,5:100 -S SWITCH_ON_IO -I IO_RUN_LATER -c -p
Time PID: 0 PID: 1 PID: 2 CPU IOs
1 RUN:io READY READY 1
2 WAITING RUN:cpu READY 1 1
3 WAITING RUN:cpu READY 1 1
4 WAITING RUN:cpu READY 1 1
5 WAITING RUN:cpu READY 1 1
6 WAITING RUN:cpu READY 1 1
7* READY DONE RUN:cpu 1
8 READY DONE RUN:cpu 1
9 READY DONE RUN:cpu 1
10 READY DONE RUN:cpu 1
11 READY DONE RUN:cpu 1
12 RUN:io_done DONE DONE 1
13 RUN:io DONE DONE 1
14 WAITING DONE DONE 1
15 WAITING DONE DONE 1
16 WAITING DONE DONE 1
17 WAITING DONE DONE 1
18 WAITING DONE DONE 1
19* RUN:io_done DONE DONE 1
20 RUN:io DONE DONE 1
21 WAITING DONE DONE 1
22 WAITING DONE DONE 1
23 WAITING DONE DONE 1
24 WAITING DONE DONE 1
25 WAITING DONE DONE 1
26* RUN:io_done DONE DONE 1
Stats: Total Time 26
Stats: CPU Busy 16 (61.54%)
Stats: IO Busy 15 (57.69%)
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在运行完第一个io操作后没有及时继续运行该进程，导致该进程后续进行io操作时浪费了时间。
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| $ ./process-run.py -l 3:0,5:100,5:100 -S SWITCH_ON_IO -I IO_RUN_IMMEDIATE -c -p
Time PID: 0 PID: 1 PID: 2 CPU IOs
1 RUN:io READY READY 1
2 WAITING RUN:cpu READY 1 1
3 WAITING RUN:cpu READY 1 1
4 WAITING RUN:cpu READY 1 1
5 WAITING RUN:cpu READY 1 1
6 WAITING RUN:cpu READY 1 1
7* RUN:io_done DONE READY 1
8 RUN:io DONE READY 1
9 WAITING DONE RUN:cpu 1 1
10 WAITING DONE RUN:cpu 1 1
11 WAITING DONE RUN:cpu 1 1
12 WAITING DONE RUN:cpu 1 1
13 WAITING DONE RUN:cpu 1 1
14* RUN:io_done DONE DONE 1
15 RUN:io DONE DONE 1
16 WAITING DONE DONE 1
17 WAITING DONE DONE 1
18 WAITING DONE DONE 1
19 WAITING DONE DONE 1
20 WAITING DONE DONE 1
21* RUN:io_done DONE DONE 1
Stats: Total Time 21
Stats: CPU Busy 16 (76.19%)
Stats: IO Busy 15 (71.43%)
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本题在6的基础上做了改善，立即运行进程，对运行时间做了优化。
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第8题是一道开放性问题，为了让读者能够理解进程运行的奥秘，请读者自行实践。