Operating Systems | Module 6: Memory Management Strategies II - Virtual Memory by Prakhar Chauhan | Learn Smarter
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Module 6: Memory Management Strategies II - Virtual Memory

Virtual memory is a sophisticated technique that enhances memory management by allowing processes to operate in an extended address space, regardless of the physical RAM available. Demand paging efficiently loads necessary pages on-demand, while page replacement algorithms optimally manage memory when faults occur. Strategies like Copy-on-Write and the Working-Set Model further reduce overhead and improve process performance while addressing issues such as thrashing and kernel memory allocation.

Sections

  • 6

    Memory Management Strategies Ii - Virtual Memory

    This section explores virtual memory, its management techniques, and the processes involved in demand paging and page replacement strategies.

    Learning Practice

  • 6.1

    Background

    Virtual memory is a memory management technique that allows programs to execute without needing all of their pages in physical memory, greatly enhancing CPU efficiency and multitasking.

    Learning Practice

  • 6.1.1

    Demand Paging

    Demand paging allows programs to load only the pages they need into memory, improving efficiency by reducing I/O operations.

    Learning Practice

  • 6.1.1.1

    How It Works

    This section explains the workings of virtual memory, highlighting demand paging, page fault handling, and the role of the operating system.

    Learning Practice

  • 6.1.1.2

    Benefits Of Demand Paging

    Demand paging enhances memory management by loading only the necessary pages into RAM, minimizing resource usage and allowing larger programs to run efficiently.

    Learning Practice

  • 6.1.2

    Page Faults

    Page faults are critical interrupts that occur when a program attempts to access a virtual memory address not currently mapped to physical memory, leading to a hardware trap that the OS must handle.

    Learning Practice

  • 6.1.2.1

    Detailed Steps Of Page Fault Handling

    This section outlines the detailed steps involved in handling page faults in virtual memory systems.

    Learning Practice

  • 6.1.3

    Copy-On-Write (Cow)

    Copy-on-Write (COW) is an optimization technique used in operating systems to improve the efficiency of process creation during the `fork()` system call by sharing memory pages until modification occurs.

    Learning Practice

  • 6.1.3.1

    Mechanism

    The mechanism of virtual memory involves demand paging and page fault handling, enabling efficient memory utilization and multitasking in computers.

    Learning Practice

  • 6.1.3.2

    Benefits

    This section outlines the key benefits of utilizing demand paging in virtual memory systems.

    Learning Practice

  • 6.2

    Page Replacement Algorithms

    Page replacement algorithms are strategies used by operating systems to manage memory by deciding which pages to remove when new pages need to be loaded into memory.

    Learning Practice

  • 6.2.1

    Fifo (First-In, First-Out)

    The FIFO page replacement algorithm evicts the oldest page in memory first, aiming to optimize memory efficiency.

    Learning Practice

  • 6.2.2

    Optimal (Opt / Min)

    The Optimal page replacement algorithm provides a theoretical standard for minimizing page faults by replacing the page that will not be used for the longest future duration.

    Learning Practice

  • 6.2.3

    Lru (Least Recently Used)

    The LRU (Least Recently Used) page replacement algorithm replaces the page that has not been used for the longest time to optimize memory utilization.

    Learning Practice

  • 6.2.4

    Counting-Based Algorithms

    Counting-based algorithms utilize the frequency of page accesses to make page replacement decisions aimed at optimizing memory usage.

    Learning Practice

  • 6.2.4.1

    Lfu (Least Frequently Used)

    The LFU algorithm is a page replacement strategy that evicts the least frequently accessed memory pages to optimize performance in a multitasking environment.

    Learning Practice

  • 6.2.4.2

    Mfu (Most Frequently Used)

    The MFU page replacement algorithm selects the page with the highest access frequency for replacement, based on the premise that a frequently used page may soon become less active.

    Learning Practice

  • 6.2.5

    Working-Set Model

    The Working-Set Model is a memory management strategy designed to minimize page faults by keeping a process's actively used pages in physical memory.

    Learning Practice

  • 6.3

    Thrashing

    Thrashing is a severe performance issue in virtual memory systems caused by excessive paging activity, leading to diminished CPU utilization and system responsiveness.

    Learning Practice

  • 6.3.1

    Causes Of Thrashing

    Thrashing occurs when a system is overwhelmed by page faults, hindering computational performance due to excessive paging.

    Learning Practice

  • 6.3.2

    Symptoms Of Thrashing

    Thrashing occurs when excessive paging leads to reduced system performance, making it difficult for processes to execute efficiently.

    Learning Practice

  • 6.3.3

    Solutions To Thrashing

    This section outlines key solutions to the performance issue of thrashing in virtual memory systems, emphasizing the need for appropriate memory management.

    Learning Practice

  • 6.4

    Allocating Kernel Memory

    Kernel memory management involves the efficient allocation of memory for system-level processes and data structures, employing specialized techniques due to unique performance demands.

    Learning Practice

  • 6.4.1

    Buddy System

    The Buddy System is an efficient memory management algorithm used in operating systems to allocate blocks of memory efficiently while reducing fragmentation.

    Learning Practice

  • 6.4.2

    Slab Allocation

    Slab allocation is an efficient memory management technique within operating system kernels designed to minimize fragmentation and improve performance when allocating fixed-size kernel objects.

    Learning Practice

References

Untitled document (14).pdf

Class Notes

Memorization

What we have learnt

  • Virtual memory allows proce...
  • Demand paging improves effi...
  • Various page replacement al...

Final Test

Revision Tests