Unformatted text preview: ed as an array of Æ contiguous byte-sized cells stored on disk. Each byte has a unique virtual address that serves as an index into the array. The contents of the array on disk are cached in main memory. As with any other cache in the memory hierarchy, the data on disk (the lower level) is partitioned into blocks that serve as the transfer units between the disk and the main memory (the upper level). VM systems handle this by partitioning the virtual memory into ﬁxed-sized blocks called Ô virtual pages (VPs). Each virtual page is È ¾ bytes in size. Similarly, physical memory is partitioned into physical pages (PPs), also È bytes in size. (Physical pages are also referred to as page frames.)
0 Physical memory
0 VP 0 VP 1 unallocated cached uncached unallocated cached uncached cached uncached empty empty empty PP 0 PP 1 VP 2n-p-1 M-1 N-1 PP 2m-p-1 Virtual pages (VP's) stored on disk Physical pages (PP's) cached in DRAM Figure 10.3: How a VM system uses main memory as a cache. At any point in time, the set of virt...
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