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However, a large page file generally allows the use of memory-heavy applications, with no penalties besides using more disk space. While a fragmented page file may not be an issue by itself, fragmentation of a variable size page file will over time create several fragmented blocks on the drive, causing other files to become fragmented.
External fragmentation also occurs in file systems as many files of different sizes are created, change size, and are deleted. The effect is even worse if a file which is divided into many small pieces is deleted, because this leaves similarly small regions of free spaces.
As a result, the last page will likely only be partially full, wasting some amount of memory. Larger page sizes lead to a large amount of wasted memory, as more potentially unused portions of memory are loaded into the main memory. Smaller page sizes ensure a closer match to the actual amount of memory required in an allocation.
However, the mark and sweep is the only strategy that readily cooperates with external allocators in the first place. A mark and don't sweep garbage collector, like the mark-and-sweep, keeps a bit with each object to record if it is white or black; the grey set is kept as a separate list or using another bit. There are two key differences here.
File system fragmentation is more problematic with consumer-grade hard disk drives because of the increasing disparity between sequential access speed and rotational latency (and to a lesser extent seek time) on which file systems are usually placed. [8] Thus, fragmentation is an important problem in file system research and design.
The fragmentation thus becomes a problem passed to programmers who may well distort their program to match certain page sizes. With segmentation, the fragmentation is external to segments (external fragmentation) and thus a system problem, which was the aim of virtual memory in the first place, to relieve programmers of such memory ...
In computer operating systems, demand paging (as opposed to anticipatory paging) is a method of virtual memory management. In a system that uses demand paging, the operating system copies a disk page into physical memory only when an attempt is made to access it and that page is not already in memory (i.e., if a page fault occurs).
The theoretically optimal page replacement algorithm (also known as OPT, clairvoyant replacement algorithm, or Bélády's optimal page replacement policy) [3] [4] [2] is an algorithm that works as follows: when a page needs to be swapped in, the operating system swaps out the page whose next use will occur farthest in the future. For example, a ...