Computer Organisation and Architecture - Vol 3 | 19. Approximate LRU Implementation by Abraham | Learn Smarter
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19. Approximate LRU Implementation

This chapter delves into various page replacement algorithms used in memory management, highlighting the limitations of exact LRU and introducing approximate LRU methods such as reference bits and sampled LRU. It discusses the clock algorithm and second chance strategies while also addressing Belady's anomaly, which challenges conventional expectations regarding page fault occurrences with increased memory frames. The chapter emphasizes the importance of efficiently managing memory references to optimize system performance.

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Sections

  • 19.1

    Approximate Lru Implementation

    Approximate LRU implementation simplifies page replacement by using reference bits to predict page usage without high hardware costs.

    Learning Practice

  • 19.1.1

    Reference Bit Mechanism

    This section discusses the reference bit mechanism for page replacement in operating systems, specifically focusing on approximate LRU and its implementation.

    Learning Practice

  • 19.1.2

    Setting Reference Bits To 0

    This section discusses the implementation of page replacement strategies using reference bits in memory management, particularly focusing on approximate LRU algorithms.

    Learning Practice

  • 19.1.3

    Replacement Page Selection

    This section discusses page replacement strategies in operating systems, focusing on approximate LRU and its implementations, including the referenced bit methods and the clock algorithm.

    Learning Practice

  • 19.1.4

    Fifo Strategy For Replacement

    The section discusses the FIFO strategy for page replacement and its relationship with hardware and software implementations, particularly focusing on the approximate LRU method.

    Learning Practice

  • 19.2

    Sampled Lru Implementation

    This section explains the implementation of sampled Least Recently Used (LRU) algorithms in operating systems, focusing on efficiency and minimization of hardware costs.

    Learning Practice

  • 19.2.1

    Reference Byte Mechanism

    This section discusses the Reference Byte Mechanism used in page replacement strategies to optimize memory management by utilizing reference bits and approximations of Least Recently Used (LRU) algorithms.

    Learning Practice

  • 19.2.2

    Clearing Reference Bits

    This section discusses the implementation of page reference bits in virtual memory management, focusing on strategies for approximating Least Recently Used (LRU) algorithms.

    Learning Practice

  • 19.2.3

    Page Replacement Based On Reference Bytes

    This section discusses various page replacement algorithms, particularly focusing on approximate methods that utilize reference bits for tracking page usage.

    Learning Practice

  • 19.3

    Clock Algorithm (Second Chance)

    The Clock Algorithm is a page replacement strategy that gives pages a 'second chance' based on their reference bit status, improving memory management efficiency.

    Learning Practice

  • 19.3.1

    Operation Of The Clock Algorithm

    The Clock Algorithm is an efficient page replacement strategy that utilizes reference bits to approximate Least Recently Used (LRU) without the high overhead of tracking exact usage.

    Learning Practice

  • 19.3.2

    Search Mechanism In Circular List

    This section discusses the implementation of approximate LRU through reference bits in page tables, focusing on search mechanisms in circular lists and related algorithms.

    Learning Practice

  • 19.4

    Dirty Pages In Replacement

    This section discusses various page replacement strategies, particularly focusing on handling dirty pages and the trade-offs of hardware and software implementations.

    Learning Practice

  • 19.4.1

    Handling Dirty Pages

    This section discusses various methods for managing dirty pages in memory, focusing on efficient page replacement strategies like approximate LRU and the clock algorithm.

    Learning Practice

  • 19.4.2

    Preference For Clean Pages

    This section discusses the implementation of approximate page replacement methods, focusing on reference bits and varying strategies to select pages for replacement.

    Learning Practice

  • 19.5

    Modified Clock Replacement Algorithm

    The Modified Clock Replacement Algorithm optimizes memory page replacement by managing reference and dirty bits to determine the best page to replace.

    Learning Practice

  • 19.5.1

    Extension With Dirty Bit

    This section discusses various page replacement algorithms, including approximate LRU, sampled LRU, and the clock algorithm, emphasizing the concept of dirty bits and how they influence page replacement decisions.

    Learning Practice

  • 19.5.2

    Replacement Strategy

    This section discusses various page replacement strategies, including approximate LRU, sampled LRU, clock, and modified clock algorithms, focusing on their implementation and efficiency.

    Learning Practice

  • 19.6

    Page Fault Analysis

    This section discusses page fault management methods, focusing on strategies like approximate LRU, sampled LRU, the clock algorithm, and the modified clock algorithm.

    Learning Practice

  • 19.6.1

    Lifo Vs Optimal Page Replacement

    This section explores various page replacement algorithms, contrasting LIFO and Optimal strategies while discussing hardware versus software implementation.

    Learning Practice

  • 19.6.2

    Calculating Page Faults

    This section discusses methods for calculating page faults in memory management, detailing various algorithms including Approximate LRU and the Clock Algorithm.

    Learning Practice

  • 19.7

    Belady’s Anomaly

    This section discusses Belady’s Anomaly, a counterintuitive situation where increasing the number of page frames results in more page faults under certain conditions when using the FIFO page replacement algorithm.

    Learning Practice

  • 19.7.1

    Description Of The Anomaly

    The section discusses approximations of the Least Recently Used (LRU) page replacement algorithm and the phenomena surrounding Belady's anomaly.

    Learning Practice

  • 19.7.2

    Example Of Fifo Replacement

    The section discusses various page replacement algorithms, particularly focusing on FIFO and its approximations like LRU and sampled LRU.

    Learning Practice

References

33 part b.pdf

Class Notes

Memorization

What we have learnt

  • Approximate LRU uses refere...
  • The clock algorithm provide...
  • Belady's anomaly illustrate...

Final Test

Revision Tests