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Modify 4-3 answer #25

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25 changes: 13 additions & 12 deletions 4/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -39,17 +39,18 @@ This program, `process-run.py`, allows you to see how process states change as p

```
$ ./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* DONE DONE

Stats: Total Time 6
Stats: CPU Busy 5 (83.33%)
Stats: IO Busy 4 (66.67%)
Time PID: 0 PID: 1 CPU IOs
1 RUN:io READY 1
2 BLOCKED RUN:cpu 1 1
3 BLOCKED RUN:cpu 1 1
4 BLOCKED RUN:cpu 1 1
5 BLOCKED RUN:cpu 1 1
6 BLOCKED DONE 1
7* RUN:io_done DONE 1

Stats: Total Time 7
Stats: CPU Busy 6 (85.71%)
Stats: IO Busy 5 (71.43%)
```

4. We’ll now explore some of the other flags. One important flag is `-S`, which determines how the system reacts when a process issues an I/O. With the flag set to `SWITCH_ON_END`, the systemwill NOT switch to another process while one is doing I/O, instead waiting until the process is completely finished. What happens when you run the following two processes (`-l 1:0,4:100 -c -S SWITCH_ON_END`), one doing I/O and the other doing CPU work?
Expand All @@ -66,4 +67,4 @@ This program, `process-run.py`, allows you to see how process states change as p

Now other proecss can run when process 0 is waiting IO. More fair and reduce response time.

8. Now run with some randomly generated processes: `-s 1 -l 3:50,3:50` or `-s 2 -l 3:50,3:50` or `-s 3 -l 3:50,3:50`. See if you can predict how the trace will turn out. What happens when you use the flag `-I IO_RUN_IMMEDIATE` vs. `-I IO_RUN_LATER`? What happens when you use `-S SWITCH_ON_IO` vs. `-S SWITCH_ON_END`?
8. Now run with some randomly generated processes: `-s 1 -l 3:50,3:50` or `-s 2 -l 3:50,3:50` or `-s 3 -l 3:50,3:50`. See if you can predict how the trace will turn out. What happens when you use the flag `-I IO_RUN_IMMEDIATE` vs. `-I IO_RUN_LATER`? What happens when you use `-S SWITCH_ON_IO` vs. `-S SWITCH_ON_END`?