Homework Assignment 2

Show all your work.

Score: 40 pts

Exercise I (2*15 = 30)

There are three processes in the scheduling queue and assume that all three of them are ready to run. Assume that P1 arrived a little before P2; and P2 arrived a little before P3. Scheduling starts at time t = 0. The CPU and I/O burst patterns of the three processes are as shown below:

Given the following processes that arrived in the order shown

	CPU Burst Time	IO Burst Time	CPU Burst Time	IO Burst Time	CPU Burst Time
P1	4	2	4	2	4
P2	5	2	5
P3	2	2	2	2	2

Each process exits the system once its CPU and I/O bursts as shown above are complete.

Show the activity in the processor and the I/O area using the FCFS, SJF, and Round Robin (time quantum = 2) algorithms

For each algorithm, compute the average waiting time, the average response time, and the throughput.

Exercise II (Time scale as shown in class = 5pts, Table below = 5pts)

Recall that Shortest Remaining Job First (SRJF) is a variant of Shortest Job First (SJF) with preemption added in. Consider the following three processes vying for the CPU. The scheduler uses SRJF. The scheduler re-evaluates which process to run only upon the arrival of a new process into the scheduling queue, or the completion of a process. The table shows the arrival time of each process.

Process	Arrival Time	Execution Time
P1	To	5 ms
P2	To + 2 ms	4 ms
P3	To + 3 ms	1 ms

The scheduling starts at time To.

Fill in the table below with the process that is executing on the processor during each time slot. Be sure to show your work as to how you arrived at schedule.

To+	0	1	2	3	4	5	6	7	8	9	10	11	12
Running