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Unformatted text preview: ual pages is partitioned into three disjoint subsets: ¯ Unallocated: Pages that have not yet been allocated (or created) by the VM system. Unallocated blocks do not have any data associated with them, and thus do not occupy any space on disk. 10.3. VM AS A TOOL FOR CACHING 489 ¯ ¯ Cached: Allocated pages that are currently cached in physical memory. Uncached: Allocated pages that are not cached in physical memory. The example in Figure 10.3 shows a small virtual memory with 8 virtual pages. Virtual pages 0 and 3 have not been allocated yet, and thus do not yet exist on disk. Virtual pages 1, 4, and 6 are cached in physical memory. Pages 2, 3, 5, and 7 are allocated, but are not currently cached in main memory. 10.3.1 DRAM Cache Organization
To help us keep the different caches in the memory hierarchy straight, we will use the term SRAM cache to denote the L1 and L2 cache memories between the CPU and main memory, and the term DRAM cache to denote the VM system’s cache that caches virtual pages in main memory. The position of the DRAM cache...
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