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Page cache. In computing, a page cache, sometimes also called disk cache, [ 1] is a transparent cache for the pages originating from a secondary storage device such as a hard disk drive (HDD) or a solid-state drive (SSD). The operating system keeps a page cache in otherwise unused portions of the main memory (RAM), resulting in quicker access ...
Memory paging. In computer operating systems, memory paging (or swapping on some Unix-like systems) is a memory management scheme by which a computer stores and retrieves data from secondary storage [ a] for use in main memory. [citation needed] In this scheme, the operating system retrieves data from secondary storage in same-size blocks ...
A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in a page table. It is the smallest unit of data for memory management in an operating system that uses virtual memory. Similarly, a page frame is the smallest fixed-length contiguous block of physical memory into which memory ...
The unified page cache operates on units of the smallest page size supported by the CPU (4 KiB in ARMv8, x86 and x86-64) with some pages of the next larger size (2 MiB in x86-64) called "huge pages" by Linux. The pages in the page cache are divided in an "active" set and an "inactive" set. Both sets keep a LRU list of pages.
Slab: slab represents a contiguous piece of memory, usually made of several virtually contiguous pages. The slab is the actual container of data associated with objects of the specific kind of the containing cache. When a program sets up a cache, it allocates a number of objects to the slabs associated with that cache.
Cache replacement policies. In computing, cache replacement policies (also known as cache replacement algorithms or cache algorithms) are optimizing instructions or algorithms which a computer program or hardware-maintained structure can utilize to manage a cache of information. Caching improves performance by keeping recent or often-used data ...
Readahead is a system call of the Linux kernel that loads a file's contents into the page cache.This prefetches the file so that when it is subsequently accessed, its contents are read from the main memory rather than from a hard disk drive (HDD), resulting in much lower file access latencies.
Linux tmpfs (previously known as shm fs) [6] is based on the ramfs code used during bootup and also uses the page cache, but unlike ramfs it supports swapping out less-used pages to swap space, as well as filesystem size and inode limits to prevent out of memory situations (defaulting to half of physical RAM and half the number of RAM pages ...