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In computer file systems, a cluster (sometimes also called allocation unit or block) is a unit of disk space allocation for files and directories.To reduce the overhead of managing on-disk data structures, the filesystem does not allocate individual disk sectors by default, but contiguous groups of sectors, called clusters.
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. For example, objects that are at least 1/8 of the page size for a given machine may benefit from a "large slab" size, with explicit free lists, while smaller objects may ...
In computer file systems, a block allocation map is a data structure used to track disk blocks that are considered "in use". Blocks may also be referred to as allocation units or clusters. [1] CP/M used a block allocation map in its directory. Each directory entry could list 8 or 16 blocks (depending on disk format) that were allocated to a file.
This work was completed in 1995 [9] and integrated into the ML Kit, a version of ML based on region allocation in place of garbage collection. This permitted a direct comparison between the two on medium-sized test programs, yielding widely varying results ("between 10 times faster and four times slower") depending on how "region-friendly" the ...
In the first variant, called bin-packing with size-increasing fragmentation (BP-SIF), each item may be fragmented; overhead units are added to the size of every fragment. In the second variant, called bin-packing with size-preserving fragmentation ( BP-SPF ) each item has a size and a cost; fragmenting an item increases its cost but does not ...
Fixed-size block memory pools do not need to store allocation metadata for each allocation, describing characteristics like the size of the allocated block. Particularly for small allocations, this provides substantial space savings. Allows deterministic behavior on real-time systems avoiding the out of memory errors. Drawbacks
The granular nature results in unused space, sometimes called slack space, for each file except for those that have the rare size that is a multiple of the granular allocation. [10] For a 512-byte allocation, the average unused space is 256 bytes. For 64 KB clusters, the average unused space is 32 KB. Generally, the allocation unit size is set ...
Block suballocation addresses this problem by dividing up a tail block in some way to allow it to store fragments from other files. Some block suballocation schemes can perform allocation at the byte level; most, however, simply divide up the block into smaller ones (the divisor usually being some power of 2). For example, if a 38 KiB file is to be stored in a file system using 32