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Dale - Computer Science Illuminated 359

Dale - Computer Science Illuminated 359 - given instance in...

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Demand paging An extension to paged memory management in which pages are brought into memory only when referenced (on demand) Page swap Bringing in one page from secondary memory, possibly causing another to be removed 332 Chapter 10 Operating Systems Figure 10.7 A paged memory manage- ment approach 0 Page P1 PMT 1 2 3 4 5 Frame 12 15 7 22 0 Frame Memory 1 2 3 4 Contents P2/Page2 P1/Page0 P1/Page3 P2/Page0 P2/Page3 P1/Page1 P1/Page2 . . . 5 6 7 8 9 10 11 12 13 14 15 0 Page P2 PMT 1 2 3 10 Frame 18 1 11 the challenge of loading a process from finding one available large chunk of space to finding enough small chunks. An important extension to the idea of paged memory management is the idea of demand paging , which takes advantage of the fact that not all parts of a program actually have to be in memory at the same time. At any
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Unformatted text preview: given instance in time, the CPU is accessing one page of a process. At that point, it doesn’t really matter if the other pages of that process are even in memory. In demand paging, the pages are brought into memory on demand. That is, when a page is referenced, we first see whether it is in memory already and, if so, complete the access. If not, the page is brought in from secondary memory into an available frame, and then the access is completed. The act of bringing in a page from secondary memory, which often causes another page to be written back to secondary memory, is called a page swap ....
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