Transcription of Virtual Memory and Address Translation
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Virtual Memory and Address Translation
Virtual Memory andAddress Translation1 ReviewProgram addresses are Virtual addresses. Relative offset of program regions can not change during program execution. , heap can not move further from Virtual addresses == physical Address inconvenient. Program location is compiled into the single offset register allows the OS to place a process Virtual Address space anywhere in physical Memory . Virtual Address space must be smaller than physical. Program is swapped out of old location and swapped into creates external fragmentation and requires large 2ggqgregions of contiguous physical Memory . We look to fixed sized units, Memory pages, to solve the MemoryConceptKey problem: How can one support programs that require more Memory than is physically available?
Realizing Virtual Memory Paging A process’s virtual address space is partitioned into equal sized pages ¾page= page frame 2n-1 = (p MAX-1,o MAX-1) page page frame (p,o) o Virtual Address Space A virtual address is a pair (p, o) p — page number (p maxpages) o — page offset (o maxbytes/pages) Virtual address = o max×p + o 7 po(0,0) p VA ...
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