OS CPU Scheduling

Question 41

Which of the following statement is true?

• Hard real time OS has less jitter than soft real time OS
• Hard real time OS has more jitter than soft real time OS
• Hard real time OS has equal jitter as soft real time OS
• None of the above

Question 42

Which of the following scheduling algorithms may cause starvation ? a. First-come-first-served b. Round Robin c. Priority d. Shortest process next e. Shortest remaining time first

• a, c and e
• c, d and e
• b, d and e
• b, c and d

Question 43

Five jobs A, B, C, D and E are waiting in Ready Queue. Their expected runtimes are 9, 6, 3, 5 and x respectively. All jobs entered in Ready queue at time zero. They must run in _____ order to minimize average response time if 3 < x < 5.

• B, A, D, E, C
• C, E, D, B, A
• E, D, C, B, A
• C, B, A, E, D

Question 44

Consider three CPU intensive processes P₁, P₂, P₃ which require 20, 10 and 30 units of time, arrive at times 1, 3 and 7 respectively. Suppose operating system is implementing Shortest Remaining Time first (preemptive scheduling) algorithm, then _____ context switches are required (suppose context switch at the beginning of Ready queue and at the end of Ready queue are not counted).

• 3
• 2
• 4
• 5

Question 45

Consider a system which have ‘n’ number of processes and ‘m’ number of resource types. The time complexity of the safety algorithm, which checks whether a system is in safe state or not, is of the order of:

• O(mn)
• O(m²n²)
• O(m²n)
• O(mn²)

Question 46

Which of the following is not an optimization criterion in the design of a CPU scheduling algorithm?

• Minimum CPU utilization
• Maximum throughput
• Minimum turnaround time
• Minimum waiting time

Question 47

A scheduling Algorithm assigns priority proportional to the waiting time of a process. Every process starts with priority zero (lowest priority). The scheduler reevaluates the process priority for every ‘T’ time units and decides next process to be scheduled. If the process have no I/O operations and all arrive at time zero, then the scheduler implements _________ criteria.

• Priority scheduling
• Round Robin Scheduling
• Shortest Job First
• FCFS

Question 48

A system has four processes and five allocatable resources. The current allocation and maximum needs are as follows:

	        Allocated	Maximum	       Available
Process A	1 0 2 1 1	1 1 2 1 3	0 0 x 1 1
Process B	2 0 1 1 0	2 2 2 1 0	
Process C	1 1 0 1 0	2 1 3 1 0	
Process D	1 1 1 1 0	1 1 2 2 1	
The smallest value of x for which the above system in safe state is __________.

• 1
• 3
• 2
• Not safe for any value of x.

Question 49

Below is the precedence graph for a set of tasks to be executed on a parallel processing system S. What is the efficiency of this precedence graph on S if each of the tasks T1, T2, T3,....T8 takes the same time and the system S has five processors?

• 25%
• 40%
• 50%
• 90%

Question 50

In a system using single processor, a new process arrives at the rate of six processes per minute and each such process requires seven seconds of service time. What is the CPU utilization?

• 70%
• 30%
• 60%
• 64%