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Chapter 13 Address Space

Chapter 13 Address Space. Chien -Chung Shen CIS, UD cshen@cis.udel.edu. Lack of M emory Abstraction. Earlier systems did not provide much of an abstraction of (physical) memory OS == library that sat in memory starting from physical address 0

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Chapter 13 Address Space

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  1. Chapter 13Address Space Chien-Chung Shen CIS, UD cshen@cis.udel.edu

  2. Lack of Memory Abstraction • Earlier systems did not provide much of an abstraction of (physical) memory • OS == library that sat in memory starting from physical address 0 • One running program that sat in memory starting from physical address 64K

  3. Multiprogramming • Multiple concurrent processes • increase utilization • time sharing & interactive • Leave processes in memory and switch between them • One critical issue • protection

  4. Address Space • Abstractionof physical memory • Running program’s view of physical memory: contain all the memory state of running program • The process is NOT in memory at physical addresses 0 through 16KB • Virtual address vs. physical address • Address spaces of threads ? • How to virtualize memory ? • How can the OS build this abstraction of a private, potentially large address space for multiple running processes (all sharing memory) on top of a single, physical memory?

  5. Goals • Transparency • virtualized memory is implemented in a way that is invisible to the running program • program behaves as if it has its own private physical memory • OS and hardware do all the work to multiplex memory among many different processes, and hence implement the illusion • Efficiency – time and space • Protection • isolation – microkernel walls off pieces of the OS from other pieces of the OS

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