Computer Science Test Template (Page 2 of 4) in pdf

9. In Linux, tasks that are not real-time have dynamic priorities that are based on their ____

values plus or minus the value 5.

A) share

B) active

C) nice

D) runqueue

Ans: C

10.

In Little's formula,

represents the ____.

average waiting time in the queue

average arrival rate for new processes in the queue

average queue length

average CPU utilization

Ans: B

11. Explain the concept of a CPU - I/O burst cycle.

Ans: The lifecycle of a process can be considered to consist of a number of bursts

belonging to two different states. All processes consist of CPU cycles and I/O

operations. Therefore, a process can be modeled as switching between bursts of

CPU execution and I/O wait.

12. What role does the dispatcher play in CPU scheduling?

Ans: The dispatcher gives control of the CPU to the process selected by the short-term

scheduler. To perform this task, a context switch, a switch to user mode, and a jump

to the proper location in the user program are all required. The dispatch should be

made as fast as possible. The time lost to the dispatcher is termed dispatch latency.

13. Explain the difference between a response time and a turnaround time. These times are

both used to measure the effectiveness of scheduling schemes.

Ans: Turnaround time is the sum of the periods that a process is spent waiting to get into

memory, waiting in the ready queue, executing on the CPU, and doing I/O.

Turnaround time essentially measures the amount of time it takes to execute a

process. Response time, on the other hand, is a measure of the time that elapses

between a request and the first response produced.

14. What effect does the size of the time quantum have on the performance of an RR

algorithm?

Ans: At one extreme, if the time quantum is extremely large, the RR policy is the same

as the FCFS policy. If the time quantum is extremely small, the RR approach is

called processor sharing and creates the appearance that each of n processes has its

own processor running at 1/n the speed of the real processor.

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