Problem
This question is about process scheduling.
A. Suppose that we are given a collection of jobs, each with an arrival time and a (known) processing time. Define what is meant by the following performance metrics of a scheduler :
a. average turnaround time (ATAT)
b. average response time (ART)
B. You have studied three scheduling algorithms: round-robin (RR), first-in-first-out (FIFO) and shortest remaining time first (SRTF).
a. give an example collection of jobs where the ATAT of RR is worse than that of SRTF
b. give an example collection of jobs where the ART of SRTF is worse than that of RR
c. give an example collection of jobs where the ART of FIFO is worse than that of SRTF
C. Explain why SRTF and RR cannot be used in a modern multi-user computer system
D. Explain how the MLFQ (multi-level feedback queue) algorithm works
E. As explained in the slides and textbook, MLFQ has five rules.
a. Rule 4 is: "once a job uses up its CPU quantum at a given level its priority is reduced (i.e., it moves down one queue)". What is the reasoning behind having this rule?
b. Rule 5 is: "After some time period S, move all the jobs in the system to the highest-priority queue ". What is the reasoning behind having this rule?