Roger Fan

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Notes
University Notes
Operating System
Chapter 9: Virtual Memory Management

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Chapter 9: Virtual Memory Management

Created: 2025-12-16
Updated: 2025-12-16

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  • Virtual Memory: separation of user logical memory from physical memory
    • extremely large process
    • increase CPU/resource utilization
    • free programmer from memory limitation
    • run programs faster -- less I/O would be needed to load or swap

Demand Paging

  • bring a page into memory only when it is needed, not bring whole process
    • less process creation time
    • less memory needed → more users
  • Valid-Invalid Bit in page table
    • (dealt by segmentation) invalid reference → abort
    • not-in-memory → Page Fault → Paging(bring page into memory)
  • pure demand paging
    • start a process with no page
    • never bring a page into memory until it's referenced
  • .