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Physical page number or Valid disk address null PTE 0 0
Physical Memory (DRAM) VP 1 PP 0
VP 2 VP 7 VP 3 Virtual address 1 1 1 0 0 0 PTE 7 1 PP 3 null Virtual Memory (disk)
VP 1 VP 2 VP 3 VP 4 VP 6 VP 7 Memory resident page table (DRAM) Figure 10.7: VM page fault (after). The page fault handler selects VP 4 as the victim and replaces it with a copy of VP 3 from disk. After the page fault handler restarts the faulting instruction, it will read the word from memory normally, without generating an exception. Virtual memory was invented in the early 1960s, long before the widening CPU-memory gap spawned SRAM caches. As a result, virtual memory systems use a different terminology from SRAM caches, even though many of the ideas are similar. In virtual memory parlance, blocks are known as pages. The activity of transferring a page between disk and memory is known as swapping or paging. Pages are swapped in (paged in) from disk to DRAM, and swapped out (paged out) from DRAM to disk. The strategy of waiting until the last moment to swap in a page, when a miss occurs, is known as demand paging. Othe...
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- Spring '10
- The American