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+18 votes
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Which of the following scheduling algorithms is non-preemptive?

  1. Round Robin
  2. First-In First-Out
  3. Multilevel Queue Scheduling
  4. Multilevel Queue Scheduling with Feedback
asked in Operating System by Veteran (59.6k points)
edited by | 1.1k views

2 Answers

+25 votes
Best answer
  1. Here we preempt when Time quantum is expired.
     
  2. We never preempt, so answer is (B) FIFO
     
  3. Here we preempt when process of higher priority arrives.
     
  4. Here we preempt when process of higher priority arrives or when time slice of higher level finishes & we need to move process to lower priority.
answered by Boss (43k points)
edited by
0
Your answer is obviously correct. However, can you give me a source for your reasoning for options C and D.

Galvin (8th ed) only says that the multilevel and multilevel feedback algorithms have an independent  scheduling algorithm for each queue, but dont specify when preemtion occurs.
0
Sir what does it mean by"when time slice of higher level finishes & we need to move process to lower priority."
0
@ rajinder singh

consider you have 3  queue  like A,B,C & each queue has own time slice 5,8,10 respectively

suppose  process P1 is executing in Queue B .but  B Queue time slice expired before finish Time slice of P1 . then you have to shift P1 process to  C Queue .
+7 votes
ans is b
answered by Boss (31.8k points)
Answer:

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