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While designing a preemptive job scheduling subsystem, an operating system manufacturer must select a scheduling strategy. Which of the following requirements is a reason why round-robin scheduling might be preferred over other scheduling strategies ?

  1.  The subsystem must minimize the number of context switches.
  2.  The subsystem must achieve optimal throughput of jobs.
  3.  The subsystem must guarantee that starvation will not occur.
  4.  The subsystem must guarantee that if job $J1$ arrives before job $J2$,  then $J1$ finishes before $J2$
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Round-robin scheduling splits up CPU time into little slices, and processes wait in a circular queue for a chance to use a slice of CPU time.

 Round-robin has the following properties:

  • Round-robin involves a good deal of context switching overhead. After each little slice of CPU time, the operating system must switch to another process  ( if more than one process is running ).  Hence Statement A is Not True.

  • Round-robin does not produce optimal throughput of jobs. Instead, the shortest-job-first (SJF) algorithm completes the largest number of jobs in a given amount of time.

          Hence statement B is False. 

  • Starvation cannot occur. That is, if a job waits long enough, it will receive some service and eventually be completed. 

          This statement is correct, RR ensure no starvation of jobs.

  • Round-robin does not guarantee that jobs will finish in the order that they arrive. For example, if job J1 requires sixty slices of CPU time and J2 requires only one slice, then J2 will finish approximately 59 time slices before J1.

           So Statement D also false.

Answer:

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