The placement determines whether the cache uses physical or virtual addressing. It may reside between the CPU and the CPU cache, between the CPU cache and primary storage memory, or between levels of a multi-level cache. The TLB references physical memory addresses in its table. The TLB is a cache of the page table that is, only a subset of its contents are stored. The page table (generally loaded in memory) keeps track of where the virtual pages are loaded in the physical memory. This space is segmented in pages of a prefixed size. The virtual memory is the space seen from a process. After the physical address is determined by the page walk, the virtual address to physical address mapping is entered into the TLB.Ī TLB has a fixed number of slots that contain page table entries, which map virtual addresses to physical addresses. The page walk is an expensive process, as it involves reading the contents of multiple memory locations and using them to compute the physical address. If the requested address is not in the TLB, it is a miss, and the translation proceeds by looking up the page table in a process called a page walk. If the requested address is present in the TLB, the CAM search yields a match quickly and the retrieved physical address can be used to access memory. The CAM search key is the virtual address and the search result is a physical address. The TLB is typically implemented as content-addressable memory (CAM). All current desktop, notebook, and server processors use a TLB to map virtual and physical address spaces, and it is nearly always present in any hardware which utilizes virtual memory. A translation lookaside buffer ( TLB) is a cache that memory management hardware uses to improve virtual address translation speed.
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