Lecture 1

Question 1

What is a CPU or IO burst?

Answer 1

A burst is when a thread is doing some activity either IO activity or CPU activity.

Question 2

What is the typical CPU burst distribution like for a process?

Answer 2

Many short CPU bursts and few long CPU bursts.

Question 3

What are the CPU bursts like for IO bound processes?

Answer 3

Many short CPU bursts.

Question 4

What are the CPU bursts like for CPU bound processes?

Answer 4

Few long CPU bursts.

Question 5

What does the CPU scheduler do?

Answer 5

Selects one of the processes in the ready queue to be executed.

Question 6

What are the ways a ready queue can be implemented?

Answer 6

FIFO queue
a priority queue
a tree
an unordered linked list.

Question 7

What is each record in the ready queue stored as ?

Answer 7

A process control block.

Question 8

What is preemptive scheduling?

Answer 8

The scheduler can interrupt the current running process, move it onto the ready or waiting queue and then chooses another process to run.

Question 9

What is non-preemptive scheduling?

Answer 9

Once a process is running it runs to completion and nothing can interrupt it.

Question 10

What is the main problem with preemptive scheduling?

Answer 10

Can result in race conditions.

Question 11

What is the main problem with non-preemptive scheduling?

Answer 11

The performance of the system suffers (poor performance)

Question 12

Which scheduling criteria do we want to maximize when developing a scheduling algorithm?

Answer 12

1. CPU utilization

2. Throughput

Question 13

Which scheduling criteria do we want to minimize when developing a scheduling algorithm?

Answer 13

1. Turnaround time
2. Waiting time
3. Response time

Question 14

What is CPU utilization?

Answer 14

Keeping the CPU as busy as possible

Question 15

Define throughput?

Answer 15

number of processes that complete their execution per time unit

Question 16

Define turnaround time

Answer 16

Total amount of time to execute a particular process

Question 17

Define the waiting time

Answer 17

Total amount of time a process has been waiting in the ready queue.

Question 18

Define Response time

Answer 18

Amount of time it takes from when a request was submitted until the first process response is produced, not output.

Question 19

What are the two advantages of the FCFS algorithm?

Answer 19

1. Simple

2. “Fair”

Question 20

What are the disadvantages of FCFS?

Answer 20

Average waiting and response time can be long.

Question 21

What is the convoy effect?

Answer 21

Convoy effect - short process queued behind long process

•Consider one CPU-bound and many I/O-bound processes