Replacement Policy Algorithms Quiz
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Replacement Policy Algorithms Quiz

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Questions and Answers

What replacement strategy was indicated as optimal in the final table?

  • First In First Out
  • Least Recently Used
  • Optimal (correct)
  • Random Replacement

    • In the given context, which page has the highest frequency of access in the stream?

  • d
  • b
  • c
  • a (correct)

    • Which frame is least accessed in the page stream when using the Least Recently Used (LRU) strategy?

  • c
  • f (correct)
  • e
  • a

    • How many times does the page 'c' result in a fault in the optimal strategy?

    <p>3</p> Signup and view all the answers

    What is the first page to cause a fault in the provided page stream?

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

    In the Clock replacement algorithm, how is a frame identified as a candidate for replacement?

    <p>It must have a use bit of 0.</p> Signup and view all the answers

    What is the main purpose of cleaning policies in memory management?

    <p>To determine when modified pages should be saved.</p> Signup and view all the answers

    What distinguishes demand cleaning from pre-cleaning in memory management?

    <p>Demand cleaning writes pages only when selected for replacement.</p> Signup and view all the answers

    What is the initial setting of the use bit for an incoming page in the Clock algorithm?

    <p>It starts as 1.</p> Signup and view all the answers

    In the FIFO replacement policy, how is page order primarily determined?

    <p>By the order of arrival.</p> Signup and view all the answers

    What is the primary goal of the LRU page replacement algorithm?

    <p>To replace the page that is least likely to be referenced in the near future</p> Signup and view all the answers

    In a scenario with three initially empty frames, which page would be replaced first when a new page needs to be loaded in LRU?

    <p>The page that is least recently used</p> Signup and view all the answers

    How does LRU compare to FIFO with respect to page faults?

    <p>LRU shows a better performance with fewer page faults than FIFO</p> Signup and view all the answers

    Which of the following statements about LRU is correct?

    <p>LRU aims to minimize the number of page faults</p> Signup and view all the answers

    What assumption is made regarding the number of frames when implementing LRU based on the provided content?

    <p>There are 3 frames, all initially empty</p> Signup and view all the answers

    Which page replacement algorithm would likely incur the most faults in the given scenario?

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

    In the context of memory management, what does 'page fault' refer to?

    <p>When a page needs to be replaced due to memory shortage</p> Signup and view all the answers

    In a FIFO page replacement algorithm with 3 frames, which page is replaced first when a page fault occurs?

    <p>The page that has been in memory the longest</p> Signup and view all the answers

    How many page faults occur in the FIFO algorithm with 3 frames for the page stream A; B; C; D; A; B; E?

    <p>9</p> Signup and view all the answers

    What is the total number of transfers made when using 4 frames in the FIFO page replacement algorithm?

    <p>10</p> Signup and view all the answers

    In the context of the given page stream with 4 frames, which page remained in memory the longest before being replaced?

    <p>Page A</p> Signup and view all the answers

    When using 3 frames, which of the following pages is replaced last in the FIFO algorithm before repeating the cycle?

    <p>Page D</p> Signup and view all the answers

    What is a major characteristic of the FIFO page replacement policy?

    <p>It is simple and easy to implement</p> Signup and view all the answers

    What is the maximum number of distinct pages that can be held in memory at once when using 3 frames?

    <p>3</p> Signup and view all the answers

    Which page would remain in memory the longest in the FIFO algorithm with 4 frames for the provided page stream?

    <p>Page A</p> Signup and view all the answers

    What does the Least Recently Used (LRU) replacement policy do?

    <p>Replaces the page that has not been referenced for the longest time</p> Signup and view all the answers

    Which replacement algorithm treats page frames as a circular buffer?

    <p>First-In-First-Out (FIFO)</p> Signup and view all the answers

    In the Clock replacement algorithm, what is the purpose of the use bit?

    <p>To signify whether the page has been referenced recently</p> Signup and view all the answers

    What happens when a page with a use bit of 1 is encountered in the Clock algorithm?

    <p>Its use bit is reset to 0</p> Signup and view all the answers

    Which of the following statements about the Optimal Replacement algorithm is true?

    <p>It selects the page that will not be referenced for the longest time</p> Signup and view all the answers

    What is one drawback of the First-In-First-Out (FIFO) algorithm?

    <p>It does not consider how recently pages have been accessed</p> Signup and view all the answers

    What is a potential issue encountered with the LRU replacement policy?

    <p>It may lead to thrashing by constantly replacing pages</p> Signup and view all the answers

    Which algorithm is noted for performing relatively poorly despite being simple to implement?

    <p>First-In-First-Out (FIFO)</p> Signup and view all the answers

    What occurs if all frames in the Clock replacement algorithm have a use bit of 1?

    <p>The pointer cycles through and resets all use bits to 0</p> Signup and view all the answers

    Which of the following best describes a benefit of using the Clock replacement algorithm?

    <p>It efficiently handles page faults without significant overhead</p> Signup and view all the answers

    Study Notes

    Replacement Policy Algorithms

    • Optimal Algorithm replaces page that is least likely to be referenced in the near future, it has the best performance.
    • Least Recently Used (LRU) Algorithm replaces the page in memory that has not been referenced for the longest time, it's based on the principle of locality.
    • First-In-First-Out (FIFO) Algorithm is the simplest to implement but performs relatively poorly.
    • Clock Algorithm requires an additional bit associated with each frame, called the use bit.
    • Initial Value of Use bit: 1, when the page is first loaded.
    • Subsequent Use Bit: 1, when the page is referenced.
    • Value when Page is Replaced: Pointer is moved to the next frame.
    • Scan for Replacement Page: OS looks for a page with use bit = 0 and the page with the use bit = 1 is reset to 0.
    • If All Use Bits = 1: The pointer cycles through the buffer, sets all use bits to 0, and replaces the page in the original position.
    • The Clock Algorithm is considered a compromise between simplicity and performance.

    Cleaning Policy

    • Cleaning Policy determines when a modified page should be written out to secondary memory.
    • Two alternatives to cleaning:
      • Demand Cleaning: A page is only written out to secondary memory when it has been selected for replacement.
      • Pre-Cleaning: Pages can be written out in batches, improving performance.

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    Related Documents

    COS122 Tutorial 7 - Oct 5-6, 2023.pdf

    Description

    Test your knowledge on various page replacement algorithms including Optimal, LRU, FIFO, and Clock. This quiz will challenge you on the principles and implementations of each algorithm, helping you understand their strengths and weaknesses in memory management.

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