ISRO2007-64, ISRO2008-50

Question

Feedback queues

• A. are very simple to implement
• B. dispatch tasks according to execution characteristics
• C. are used to favour real time tasks
• D. require manual intervention to implement properly

Answer 1

Answer : Dispatch tasks according to execution characteristics

Why ?

Considering feedback queue as multilevel feedback queue, we can go ahead. For each level a different or maybe same time quanta is set which is at last followed by FCFS. So tasks are dispatched according to the execution characteristics.

This scheduling algorithm is intended to meet the following design requirements for multi-mode systems:

Give preference to short jobs.
Give preference to I/O bound processes.
Separate processes into categories based on their need for the processor.

 Multilevel feedback queue scheduling allows a process to move between queues. This movement is facilitated by the characteristic of the CPU burst of the process. If a process uses too much CPU time, it will be moved to a lower-priority queue.

For Better Understanding refer this : https://en.wikipedia.org/wiki/Multilevel_feedback_queue

Answer 2

Ans B) It executes tasks according to execution characteristics. Because if it implements in  priority scheduling it takes feedback from previous level queue , and then process and executes

(C) is not true . It is not very fast like real time tasks

(D) Not needed manual intervention .Time Sharing Schedular implements this algorithm

More details here

Answer 3

(C) are used to fever real time tasks

is true.