Simulator
This lesson explains how to run the simulator which mimics some aspects of an operating system to help you solidify your understanding.
We'll cover the following...
The 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).
As described in the chapter, processes can be in a few different states:
-
RUNNING- the process is using the CPU right now -
READY- the process could be using the CPU right now but (alas) some other process is -
WAITING- the process is waiting on I/O (e.g., it issued a request to a disk) -
DONE- the process is finished executing
To run the program and get its options, do this in the terminal provided below:
prompt> ./process-run.py -h
If this doesn’t work, type “python” before the command, like this:
prompt> python process-run.py -h
What you should see is this:
Usage: process-run.py [options
Options:
-h, --help show this help message and exit
-s SEED, --seed=SEED the random seed
-l PROCESS_LIST, --processlist=PROCESS_LIST
a comma-separated list of processes to run, in the
form X1:Y1,X2:Y2,... where X is the number of
instructions that process should run, and Y the
chances (from 0 to 100) that an instruction will use
the CPU or issue an IO
-L IO_LENGTH, --iolength=IO_LENGTH
how long an IO takes
-S PROCESS_SWITCH_BEHAVIOR, --switch=PROCESS_SWITCH_BEHAVIOR