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?
Page fault handling analysis To understand the overhead of paging, compute the effective memory access time (EAT) ¾EAT = memory access time×probability of a page hit+ page fault service time×probability of a page fault Example: ¾Memory access time: 60 ns ¾Disk access time: 25 ms ¾Let p = the probability of a page fault ¾EAT = 60(1 –p ...
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