Betriebssysteme/hw1/simu2/QUESTIONS.md

Questions 4-Process-Run Simulation Part 2

This program, process-run.py, allows you to see how process states change as programs run and either use the CPU (e.g., perform an add instruction) or do I/O (e.g., send a request to a disk and wait for it to complete). See the README for details.

Please answer the questions, by giving the result and an explanation, why you got the result. Sometimes it could be helpful, if you compare your result with results of earlier questions. Write your answers in markdown syntax in the new file ANSWERS.md.

1. One important behavior is what to do when an I/O completes. With -I IO_RUN_LATER, when an I/O completes, the process that issued it is not necessarily run right away; rather, whatever was running at the time keeps running. What happens when you run this combination of processes?

./process-run.py -l 3:0,5:100,5:100,5:100 -S SWITCH ON IO -I IO RUN LATER -c -p

Are system resources being effectively utilized?

1. Now run the same processes, but with -I IO_RUN_IMMEDIATE set, which immediately runs the process that issued the I/O. How does this behavior differ? Why might running a process that just completed an I/O again be a good idea?

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