Operating System Concepts: CPU Scheduling
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Questions and Answers

What does t_n represent in the given formula?

  • alpha value for the weighting function
  • predicted value for the next CPU burst
  • actual length of nth CPU burst (correct)
  • predicted value for the current CPU burst

    • What is the range of values for alpha (α)?

  • 0 ≤ α ≤ 0.5
  • -1 ≤ α ≤ 0
  • 0 ≤ α ≤ 1 (correct)
  • 0.5 ≤ α ≤ 1

    • What is τ_(n+1) in the given formula?

  • actual length of nth CPU burst
  • predicted value for the next CPU burst (correct)
  • predicted value for the current CPU burst
  • alpha value for the weighting function

    • What is the purpose of the alpha (α) value?

    <p>to weigh the importance of the current CPU burst</p> Signup and view all the answers

    What is the formula to calculate τ_(n+1)?

    <p>τ_(n+1) = α t_n + (1- α) τ_n</p> Signup and view all the answers

    What is the relationship between τ_(n+1) and t_n?

    <p>τ_(n+1) is a weighted average of t_n and τ_n</p> Signup and view all the answers

    What is the weighting factor in the formula?

    <p>α</p> Signup and view all the answers

    What is the predicted value for the next CPU burst based on?

    <p>a weighted average of the current and previous CPU bursts</p> Signup and view all the answers

    What does the value of α close to 0 imply?

    <p>the predicted value is heavily influenced by the previous CPU burst</p> Signup and view all the answers

    What is the benefit of using a weighted average for prediction?

    <p>it allows for a more balanced prediction by considering both current and previous CPU bursts</p> Signup and view all the answers

    Study Notes

    CPU Scheduling

    • CPU Scheduling is the basis of multi-programmed operating systems, achieving efficiency and productivity by switching the CPU among processes.
    • The short-term scheduler assigns the CPU to the current process in the Ready Queue.

    Process/CPU and I/O Burst Cycle

    • For scheduling purposes, both long-term and short-term schedulers are necessary.
    • The method used to determine which queue a process will enter when it needs service is crucial.

    Multilevel Feedback Queue (MFQ)

    • An MFQ has three queues: Q0, Q1, and Q2.
    • Q0: Round Robin (RR) with a time quantum of 8 milliseconds.
    • Q1: RR with a time quantum of 16 milliseconds.
    • Q2: First-Come-First-Served (FCFS).

    Scheduling Process

    • A new job enters queue Q0, which is served FCFS, and receives 8 milliseconds of CPU time.
    • If the job doesn't finish in 8 milliseconds, it is moved to queue Q1.
    • In Q1, the job is served FCFS and receives 16 additional milliseconds.
    • If the job still doesn't complete, it is preempted and moved to queue Q2.

    CPU Burst Prediction

    • τn = actual length of the nth CPU burst.
    • τn+1 = predicted value for the next CPU burst.
    • α, 0 ≤ α ≤ 1, is a parameter used to define the prediction.
    • τn+1 = αtn + (1-α)τn is the formula used to predict the next CPU burst.

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    Description

    This quiz covers the basics of CPU scheduling, a fundamental concept in multi-programmed operating systems. It explores how CPU scheduling enhances system efficiency and productivity.

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