Assigned: Apr 5, 2020
Due: Apr 19, 2020 23:59:59
Submit: Upload to Canvas as PDF
100 points total

Problem 1 (40 points)

Consider the following set of processes:

Perform FCFS, RR \left(q=4\right), SPF, SRT, on them and get the Finish Time and Turnaround Time for each process. For reference:

• FCFS: First Come First Served
• RR: Round Robin
• SPF: Shortest Process (Job) First
• SRT: Shortest Remaining Time First

Problem 2 (20 points)

Consider a computer with two processes, H, with high priority, and L, with low priority. The scheduling rules are such that H is run whenever it is in ready state. At a certain moment, with L in its critical region, H becomes ready to run (e.g., an I/O operation completes). H now begins busy waiting, but since L is never scheduled with H is running, L never gets the chance to leave its critical region, so H loops forever. This situation is sometimes referred to as the priority inversion problem.

If instead of priority scheduling, we use round-robin scheduling, will we encounter the same problem? Please explain your answer in detail.

Problem 3 (40 points)

Based on measurements, we know for a certain system the average process runs for a time X before blocking on I/O. It takes a time Y to do a process switch, which is effectively wasted (overhead). For round-robin scheduling with quantum Q, give a formula for the CPU efficiency for each of the following:

• Q=\infty
• Q>X
• Y<Q<X
• Q=Y
• Q\longrightarrow 0, Q\ne 0

NOTE: The CPU efficiency is the useful CPU time divided by the total CPU time.