Lecture 03 - Memory Management, Virtual Memory

Lecture 03 - Memory Management, Virtual Memory -...

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Understanding Operating Systems Fifth Edition Chapter 3 Memory Management: Virtual Memory
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Understanding Operating Systems, Sixth Edition Learning Objectives After completing this chapter, you should be able to describe: The basic functionality of the memory allocation methods covered in this chapter: paged, demand paging, segmented, and segmented/demand paged memory allocation The influence that these page allocation methods have had on virtual memory 2
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Understanding Operating Systems, Sixth Edition Learning Objectives (cont'd.) The difference between a first-in first-out page replacement policy, a least-recently-used page replacement policy, and a clock page replacement policy The mechanics of paging and how a memory allocation scheme determines which pages should be swapped out of memory 3
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Understanding Operating Systems, Sixth Edition Learning Objectives (cont'd.) The concept of the working set and how it is used in memory allocation schemes The impact that virtual memory had on multiprogramming Cache memory and its role in improving system response time 4
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Understanding Operating Systems, Sixth Edition Introduction Evolution of virtual memory Paged, demand paging, segmented, segmented/demand paging Foundation for current virtual memory methods Improvement areas Need for continuous program storage Need for placement of entire program in memory during execution Fragmentation Overhead due to relocation 5
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Understanding Operating Systems, Sixth Edition Introduction (cont'd.) Page replacement policies First-In First-Out Least Recently Used Clock replacement and bit-shifting Mechanics of paging The working set Virtual memory Concepts and advantages Cache memory Concepts and advantages 6
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Understanding Operating Systems, Sixth Edition Paged Memory Allocation Before a job is loaded into memory, it is divided into parts called pages that will be loaded into memory locations called page frames. Paged Memory Allocation is based on the concept of dividing each incoming job into pages of equal size. Some OS choose a page size that is the same as the memory block size and that is also the same size as the sections of disk on which the job is stored. 7
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Paged Memory Allocation Before executing a program, the Memory Manager prepares it by: Determining the number of pages in program; Locating enough empty page frames in main memory; Loading all the program’s pages into page frames. When the program is initially prepared for loading, its pages are in logical sequence. The program pages, however, do not have to be loaded in adjacent memory. Each page can be stored in any available page
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Lecture 03 - Memory Management, Virtual Memory -...

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