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Virtual memory systems abstract between physical RAM and virtual addresses, assigning virtual memory addresses both to physical RAM and to disk-based storage, expanding addressable memory, but at the cost of speed. NUMA and SMP architectures optimize memory allocation within multi-processor systems. While these technologies dynamically manage ...
By reducing the I/O activity caused by paging requests, virtual memory compression can produce overall performance improvements. The degree of performance improvement depends on a variety of factors, including the availability of any compression co-processors, spare bandwidth on the CPU, speed of the I/O channel, speed of the physical memory, and the compressibility of the physical memory ...
Paged memory, often used for virtual memory management, is memory stored in secondary storage such as a hard disk, and is an extension to the memory hierarchy which allows use of a potentially larger storage space, at the cost of much higher latency, typically around 1000 times slower than a cache miss for a value in RAM. [8]
Virtual memory combines active RAM and inactive memory on DASD [a] to form a large range of contiguous addresses.. In computing, virtual memory, or virtual storage, [b] is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" [3] which "creates the illusion to users of a very large (main) memory".
A common optimization for physically addressed caches is to perform the TLB lookup in parallel with the cache access. Upon each virtual memory reference, the hardware checks the TLB to see whether the page number is held therein. If yes, it is a TLB hit, and the translation is made. The frame number is returned and is used to access the memory.
Non-uniform memory access (NUMA) is a computer memory design used in multiprocessing, where the memory access time depends on the memory location relative to the processor. Under NUMA, a processor can access its own local memory faster than non-local memory (memory local to another processor or memory shared between processors). [ 1 ]
Due to the higher speeds of RAM compared to disk storage, tmpfs allows cache to be much faster when stored in one, leading to a more efficient overall system, though operating systems with a page cache will see less benefit as recently-used file pages will remain in-memory if free memory is sufficient. Since RAM is cleared upon reboot, tmpfs ...
A few computers have a main memory larger than the virtual address space of a process, such as the Magic-1, [34] some PDP-11 machines, and some systems using 32-bit x86 processors with Physical Address Extension. This nullifies a significant advantage of paging, since a single process cannot use more main memory than the amount of its virtual ...