Homework 2 Sarah Diesburg Operating Systems COP 4610
Why does OS loader set kernel mode? OS needs to run with full privileges Sets more restrictive user mode bit for user programs Protects OS from errant user programs
Three Processes Process A Process B Process C Time
First In, First Out Process A Process B Process C FIFO Time BCA
First In, First Out Process A Process B Process C FIFO Average response time = [(300-50) + ( ) + 0]/3 = 200 Time BCA
First In, First Out Process A Process B Process C FIFO Average wait time = [(300-50) + ( ) + 0]/3 = 200 Time BCA
First In, First Out Process A Process B Process C FIFO Average turnaround time = [(500-50) + ( ) + (300-0)]/3 = 500 Time BABCA
Round Robin (Time slice = 100) Process A Process B Process C RR Time C
Process A Process B Process C RR Round Robin (Time slice = 100) Time C
Process A Process B Process C RR Round Robin (Time slice = 100) Time CA
Process A Process B Process C RR Round Robin (Time slice = 100) Time CA
Process A Process B Process C RR Round Robin (Time slice = 100) Time CAC
Process A Process B Process C RR Round Robin (Time slice = 100) Time CAC
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACB
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACB
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACBA
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACBA
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACBAC
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACBAC
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACBACB
Process A Process B Process C RR Round Robin (Time slice = 100) Time CACBACB
Process A Process B Process C RR Average response time = [(100-50) + (300 – 150) + 0]/3 = 66.7 Round Robin (Time slice = 100) Time CACBACB
Process A Process B Process C RR Average wait time = {[(100–50) + (400–200)] + [(300–150) + (600–400)] + [0 + (200–100) + (500–300)]}/3 = [ ]/3 = 300 Round Robin (Time slice = 100) Time CACBACB
Process A Process B Process C RR Average turnaround time = [(500 – 50) + (900 – 150) + (600 – 0)]/3 = 600 Round Robin (Time slice = 100) Time CACBACB
Shortest Job Next Process A Process B Process C SJN Time C
Shortest Job Next Process A Process B Process C SJN Time C
Shortest Job Next Process A Process B Process C SJN Time CA
Shortest Job Next Process A Process B Process C SJN Time CA
Shortest Job Next Process A Process B Process C SJN Time CA
Shortest Job Next Process A Process B Process C SJN Time CAB
Shortest Job Next Process A Process B Process C SJN Time CAB
Shortest Job Next Process A Process B Process C SJN Average response time = [(300-50) + ( ) + 0]/3 = 200 Time CAB
Shortest Job Next Process A Process B Process C SJN Average wait time = [(300-50) + ( ) + 0]/3 = 200 Time CAB
Shortest Job Next Process A Process B Process C SJN Average turnaround time = [(500-50) + ( ) + (300-0)]/3 = 500 Time CAB
Shortest Remaining Time First Process A Process B Process C SRTF Time C
Shortest Remaining Time First Process A Process B Process C SRTF Time C
Shortest Remaining Time First Process A Process B Process C SRTF Time CA
Shortest Remaining Time First Process A Process B Process C SRTF Time CA
Shortest Remaining Time First Process A Process B Process C SRTF Time CAC
Shortest Remaining Time First Process A Process B Process C SRTF Time CAC
Shortest Remaining Time First Process A Process B Process C SRTF Time CACB
Shortest Remaining Time First Process A Process B Process C SRTF Time CACB
Shortest Remaining Time First Process A Process B Process C SRTF Average response time = [0 + ( ) + 0]/3 = 117 Time CACB
Shortest Remaining Time First Process A Process B Process C SRTF Average wait time = [0 + (500 – 150) + (250 – 50)]/3 = 183 Time CACB
Shortest Remaining Time First Process A Process B Process C SRTF Average turnaround time = [(250 – 50) + (900 – 150) + (500 – 0)]/3 = 483 Time CACB