CS 3733 Operating Systems, Fall 2004 Recitation Session 10

Week of November 8.
In this session you will become familiar disk head scheduling simulator.

1. Create a Rec10 directory.
2. Download the tar file and untar it into the Rec10 directory.
3. Execute the rundisk script to start the simulator.
   
4. If all goes well you will see the main simulator window appear.
   Exit the simulator using the quit button in the upper right corner.
5. Go through the simulator tutorial that you can find here.
   Make sure you have edited the diskheadconfig file so that it has your name instead of New User.
6. Next we will perform a new experiment. Edit the diskheadconfig file and change myrun to myrun1 and myexp to myexp1.
7. Now copy myrun.run into myrun1.run and myexp.exp into myexp1.exp.
8. Edit myrun1.run, changing the first line to
   name myrun1. Also change the second line to reference myrun1 instead of myrun
9. Edit myexp1.exp, changing the first line to
   name myexp1
   and changing all occurrences of myrun to myrun1.
10. Run the simulator again. It should give exactly the same results as before.
11. Exit the simulator. We will now change the experiment. Edit the myrun1.run file and make the following changes:
    • In the first nextBlock line change 30 to 10.
    • In the first numBlocks line change 20 to 50.
    • In the second interAttival line change 5 to 1 and 15 to 3
      The line should now read:
      interArrival uniform 1 3
    • In the second numBlocks line change 4 to 50.
12. Edit myexp1.exp and add a line at the end to perform a 4th run, using the LOOK algorithm. The simplest way to do this is to duplicate the last line of the file and change both C-LOOK and CLOOK to LOOK.
13. Run the simulator again. When the run is done, click the Show Table Data button. Make sure there were 4 runs, each having 100 seeks. (Check the Count column.) Which algorithm(s) perform the best? You should see a big diffrence between one of the algorithms and the other ones. Try to understand why by looking at the information in the table and the graphs displayed by the Show Run Data Graph button.
14. Create a log file containing the table data and the graphs of the four runs. If you can, insert an explanation of why you think some of the algorithms performed a lot better than others. This explanation should appear at the end of your log file.
15. Copy the logfile.html and the .gif files into a directory under your course web page and put a link to the log file on your course web page. Make sure you can display the log file using the link on your web page and that all of the graphs appear correctly.
16. Make sure the TA has seen that you have done this.