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Which of the following statement(s) is/are correct in the context of $\text{CPU}$ scheduling?

  1. Turnaround time includes waiting time
  2. The goal is to only maximize $\text{CPU}$ utilization and minimize throughput
  3. Round-robin policy can be used even when the $\text{CPU}$ time required by each of the processes is not known apriori
  4. Implementing preemptive scheduling needs hardware support
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  1. Turnaround time includes waiting time
    • TRUE. $\text{Turnaround Time} = \text{Waiting Time} + \text{Burst Time}$
  2. The goal is to only maximize CPU utilization and minimize throughput
    • FALSE. CPU scheduling must aim to maximize CPU utilization as well as throughput. Throughput of CPU scheduling is defined as the number of processes completed in unit time. $\textsf{SJF}$ scheduling gives the highest throughput. 
  3. Round-robin policy can be used even when the CPU time required by each of the processes is not known apriori
    • TRUE. Round-robin scheduling gives a fixed time quantum to each process and for this there is no requirement to know the CPU time of the process apriori (which is not the case say for shortest remaining time first).
  4. Implementing preemptive scheduling needs hardware support
    • TRUE. Preemptive scheduling needs hardware support to manage context switch which includes saving the execution state of the current process and then loading the next process.

Correct Answer: A;C;D

Reference: Stanford Notes

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Ans. A,C and D
A. turnaround time =completion time(burst+waiting)-arrival time.
B. The goal is to maximize throughput not to minimize it.
C. Round Robin is used in modern day systems as it doesn’t requires the information about the CPU time for processes rather it works just by providing same time quanta to every process.
D. Hardware support is essential for preemption.
Answer:

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