CS 3733 Operating Systems, Fall 2004 Assignment 2 Comments

General Comments:

• This assignment was graded on a basis of 30 points.
• Each of Parts 1 and 2 were worth 5 points.
• Only a small number of students gave a reasonable answer to part 3a, so I generally did not take off for this part, but gave extra credit to those who said something that was close.
• The general idea is that the average waiting time is smaller when the short jobs are handled before the long ones.
• The idea for Part 3a is that decreasing the quantum improves the average waiting time if there are long jobs in the queue ahead of short jobs.
  It has the opposite effect if the short jobs are ahead of the long ones, as reducing the quantum delays the shorter jobs from finishing.
• For Parts 3b and 3c, you needed to run with decreasing values of the quantum, starting with the largest CPU burst.
• If the CPU quantum is larger than the largest CPU burst, it has no effect.
• You should not run the simulator with a duration smaller than the CPU burst. See this note about the simulator.
• For Part 3d, you needed to compute the total waiting time, T, the number of context switches, n, and the load average, L, for each of the two experiments. If x is the context switch time, compute T + nxL for each of the experiments, set them equal, and solve for x.