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Memory-mapped file, also known as mmap() Memory-mapped I/O, an alternative to port I/O; a communication between CPU and peripheral device using the same instructions, and same bus, as between CPU and memory; Virtual memory, technique which gives an application program the impression that it has contiguous working memory, while in fact it is ...
A memory-mapped file is a segment of virtual memory [1] that has been assigned a direct byte-for-byte correlation with some portion of a file or file-like resource. This resource is typically a file that is physically present on disk, but can also be a device, shared memory object, or other resource that an operating system can reference through a file descriptor.
In computer science, a memory map is a structure of data (which usually resides in memory itself) that indicates how memory is laid out. The term "memory map" has different meanings in different contexts. It is the fastest and most flexible cache organization that uses an associative memory. The associative memory stores both the address and ...
Memory-mapped I/O is preferred in IA-32 and x86-64 based architectures because the instructions that perform port-based I/O are limited to one register: EAX, AX, and AL are the only registers that data can be moved into or out of, and either a byte-sized immediate value in the instruction or a value in register DX determines which port is the source or destination port of the transfer.
File-backed mapping maps an area of the process's virtual memory to files; that is, reading those areas of memory causes the file to be read. It is the default mapping type. Anonymous mapping maps an area of the process's virtual memory not backed by any file, made available via the MAP_ANONYMOUS/MAP_ANON flags.
The TLB is of limited size, and when it cannot satisfy a given request (a TLB miss) the page tables must be searched manually (either in hardware or software, depending on the architecture) for the correct mapping. Larger page sizes mean that a TLB cache of the same size can keep track of larger amounts of memory, which avoids the costly TLB ...
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A block of memory cannot necessarily be placed at an arbitrary location in the cache; it may be restricted to a particular cache line or a set of cache lines [1] by the cache's placement policy. [2] [3] There are three different policies available for placement of a memory block in the cache: direct-mapped, fully associative, and set-associative.