Internal fragmentation
In computer science, internal fragmentation or scrap - in the case of hard disks Slack Space - is the effect that some memory blocks can only be partially filled when data is split up.
Another effect that leads to inefficient use of memory is external fragmentation .
description
For memory management use computer systems different methods to classify him. This relates to volatile (e.g. main memory ) as well as persistent storage (e.g. hard drives ). All methods use segmentation , paging, or a combination of both to organize memory as efficiently as possible.
With page division, the memory is divided into fixed-size pages . As soon as a program requests ( allocated ) memory , so many pages are reserved that the sum of their memory is greater than or equal to the memory requested. If the reserved memory is larger than the requested one, this difference is called internal fragmentation : this scrap lies within the reserved area, typically at the end.
Typical memory resources in information technology that are affected by internal fragmentation include: a .:
- Memory allocation by the operating system , fixed block sizes
- File creation, file systems and hard disks have fixed clusters of a few kByte in size
- IP addresses can also only be reserved in blocks of a certain size (this is why many IPs are reserved but not in active use). This effect contributes to the IPv4 address shortage.
- English text is often a byte stored per letter, although in ASCII - character encoding the most significant bit of each byte 0th A reservation of 7 bits would be functionally sufficient, so there is a waste of one bit per letter.
example
The operating system manages the main memory in pages with a size of 4 kilobytes. A program requests 5 kByte; the operating system then reserves 2 pages (= 8 kByte). The internal fragmentation is then (8-5) kByte = 3 kByte.
Individual evidence
- ↑ Jennifer Bayuk: CyberForensics: Understanding Information Security Investigations . Springer Science & Business Media, 2010, ISBN 978-1-60761-772-3 ( google.de [accessed March 17, 2017]).