OS CPU Scheduling

Question 31

Assume every process requires 3 seconds of service time in a system with single processor. If new processes are arriving at the rate of 10 processes per minute, then estimate the fraction of time CPU is busy in system?

• 20%
• 30%
• 50%
• 60%

Question 32

Consider n processes sharing the CPU in a round-robin fashion. Assuming that each process switch takes s seconds, what must be the quantum size q such that the overhead resulting from process switching is minimized but, at the same time, each process is guaranteed to get its turn at the CPU at least every t seconds ?

• a
• b
• c
• d

Question 33

Answer the following: a. Four jobs are waiting to be run. Their expected run times are 6, 3, 5 and x. In what order should they be run to minimize the average response time? b. Write a concurrent program using par begin - par end to represent the precedence graph shown below. 

[caption width="800"]Precedence graph[/caption]

• No Option provided (Subjective Question)
  Please click here for answer.

Question 34

The correct matching for the following pairs is

(A) Disk Scheduling        (1) Round robin
(B) Batch Processing       (2) SCAN
(C) Time sharing           (3) LIFO
(D) Interrupt processing   (4) FIFO

Codes:
    A   B   C   D
a   3   4   2   1
b   4   3   2   1
c   2   4   1   3
d   3   4   3   2

• a
• b
• c
• d

Question 35

When an interrupt occurs, an operating system

• ignores the interrupt
• always changes state of interrupted process to \'blocked\' and schedules another process
• always resumes execution of interrupted process after processing the interrupt
• may change the state of interrupted process to \'blocked\'and schedule another process

Question 36

Four jobs to be executed on a single processor system arrive at time 0 in the order A, B, C, D. Their burst CPU time requirements are 4, 1, 8, 1 time units respectively. The completion time of A under round robin scheduling with time slice of one time unit is

• 10
• 4
• 8
• 9

Question 37

Consider the following CPU processes with arrival times (in milliseconds) and length of CPU bursts (in milliseconds) except for process P4 as given below:

Process	Arrival Time	Burst Time
P1	   0	          5
P2	   1	          1
P3	   3	          3
P4	   4	          x

If the average waiting time across all processes is 2 milliseconds and pre-emptive shortest remaining time first scheduling algorithm is used to schedule the processes, then find the value of x ?

• 1
• 2
• 4
• None of these

Question 38

Which module gives control of the CPU to the process selected by the short - term schedular ?

• Dispatcher
• Interrupt
• Schedular
• Threading

Question 39

Consider the following scheduling

A. Gang scheduling	s. Guaranteed scheduling
B. Rate Monotonic scheduling	t. Thread scheduling
C. Fair share scheduling	u. Real time scheduling

Matching the table in the order A, B, C gives

• t, u, s
• s, t, u
• u, s, t
• u, t, s

Question 40

Consider the following four processes with the arrival time and length of CPU burst given in milliseconds : The average waiting time for preemptive SJF scheduling algorithm is __________.

• 6.5
• 7.5
• 6.75
• 7.75