Computer Organisation and Architecture - Vol 3 | 20. Belady's Anomaly by Abraham | Learn Smarter
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20. Belady's Anomaly

The discussion centers around page replacement strategies in memory management, particularly exploring Belady’s anomaly, which occurs when an increased number of page frames leads to more page faults. Key algorithms such as LRU (Least Recently Used) and optimal algorithms are presented, highlighting their inability to exhibit Belady’s anomaly as they adaptively manage recently accessed pages. The chapter further delves into memory allocation strategies for processes and addresses concepts like page buffering and thrashing.

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Sections

  • 20.1

    Belady's Anomaly

    Belady's anomaly describes a situation where increasing the number of page frames in memory can lead to an increase in the number of page faults.

    Learning Practice

  • 20.1.1

    Understanding Belady's Anomaly

    Belady's Anomaly illustrates the counterintuitive behavior in paging when increasing frames can lead to more page faults.

    Learning Practice

  • 20.1.2

    Example Of Page References

    Belady's anomaly illustrates how increasing the number of frames can lead to more page faults, challenging the intuition behind memory management.

    Learning Practice

  • 20.1.3

    Comparison Of Frames

    This section discusses Belady's anomaly and the characteristics of different page replacement algorithms, specifically optimal and LRU.

    Learning Practice

  • 20.2

    Optimal Algorithm And Lru

    This section discusses Belady's anomaly in page replacement algorithms and introduces the Optimal and Least Recently Used (LRU) algorithms, which prevent this anomaly in memory management.

    Learning Practice

  • 20.2.1

    Explanation Of Optimal Algorithm

    This section examines the concept of the optimal algorithm in the context of page replacement, particularly focusing on Belady’s anomaly.

    Learning Practice

  • 20.2.2

    Explanation Of Lru

    This section explains Belady’s anomaly, illustrating how the Least Recently Used (LRU) caching algorithm avoids such phenomena while managing page frames efficiently.

    Learning Practice

  • 20.2.3

    Why These Algorithms Avoid Belady's Anomaly

    This section explains why certain page replacement algorithms, like LRU and Optimal, avoid Belady's anomaly by maintaining the most recently used pages.

    Learning Practice

  • 20.3

    Page Buffering

    This section explains the concept of page buffering, its significance in optimizing memory management and reducing page faults during replacements.

    Learning Practice

  • 20.3.1

    Introduction To Page Buffering

    This section provides an overview of page buffering in memory management, highlighting Belady’s anomaly and various algorithms to optimize page replacements.

    Learning Practice

  • 20.3.2

    Replacing Pages And Maintaining Free Frames

    This section discusses Belady’s anomaly, the impact of frame allocation on page faults, and methods to manage free frames effectively.

    Learning Practice

  • 20.3.3

    Maintaining Clean Pages In Free Frame Pool

    This section discusses Belady’s anomaly in page replacement algorithms and the concepts of page buffering and frame allocation.

    Learning Practice

  • 20.4

    Allocation Of Frames

    This section explores Belady’s anomaly and its implications, different frame allocation strategies, and how page buffering enhances memory management.

    Learning Practice

  • 20.4.1

    Frame Allocation Strategies

    This section discusses frame allocation strategies in memory management, focusing on Belady's anomaly and various page replacement algorithms.

    Learning Practice

  • 20.4.2

    Fixed Allocation Scheme

    The fixed allocation scheme divides memory frames among processes evenly, leading to potential inefficiencies in memory usage.

    Learning Practice

  • 20.4.2.1

    Description Of Fixed Allocation

    Belady’s anomaly illustrates unexpected behavior in page replacement, where increasing the number of frames may actually lead to more page faults in certain algorithms.

    Learning Practice

  • 20.4.3

    Proportional Allocation Scheme

    The proportional allocation scheme allocates memory frames to processes based on their size, addressing Belady's anomaly.

    Learning Practice

  • 20.4.4

    Priority Based Allocation

    This section explores Belady's anomaly in page replacement algorithms and the concepts of optimal and LRU page allocation strategies, including priority-based allocation.

    Learning Practice

  • 20.5

    Concept Of Thrashing

    Thrashing occurs when a system spends excessive time paging, resulting in poor performance.

    Learning Practice

References

33 part c.pdf

Class Notes

Memorization

What we have learnt

  • Belady's anomaly occurs whe...
  • LRU and optimal algorithms ...
  • Different memory allocation...

Final Test

Revision Tests