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There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity. Analogous phenomena occur for other resources such as processors; see below.
Operating systems may use different slab sizes and internal layouts depending on the size of the objects to be stored. The reason for the large slabs having a different layout from the small slabs is that it allows large slabs to pack better into page-size units, which helps with fragmentation.
In a system using segmentation, computer memory addresses consist of a segment id and an offset within the segment. [3] A hardware memory management unit (MMU) is responsible for translating the segment and offset into a physical address, and for performing checks to make sure the translation can be done and that the reference to that segment and offset is permitted.
However, there still exists the problem of internal fragmentation – memory wasted because the memory requested is a little larger than a small block, but a lot smaller than a large block. Because of the way the buddy memory allocation technique works, a program that requests 66 K of memory would be allocated 128 K, which results in a waste of ...
Typically, an operating system assigns each program its own virtual address space. [3] A paged MMU also mitigates the problem of external fragmentation of memory. After blocks of memory have been allocated and freed, the free memory may become fragmented (discontinuous) so that the largest contiguous block of free memory may be much smaller ...
But as file sizes are often not multiples of the file system block size, this design inherently results in the last blocks of files (called tails) occupying only a part of the block, resulting in what is called internal fragmentation (not to be confused with external fragmentation). This waste of space can be significant if the file system ...
Region-based memory management works best when the number of regions is relatively small and each contains many objects; programs that contain many sparse regions will exhibit internal fragmentation, leading to wasted memory and a time overhead for region management. Again, in the presence of region inference this problem can be more difficult ...
The FAT file system is a file system used on MS-DOS and Windows 9x family of operating systems. [3] It continues to be used on mobile devices and embedded systems, and thus is a well-suited file system for data exchange between computers and devices of almost any type and age from 1981 through to the present.