Concept
Memory paging
Concepts associés (38)
Atlas (computer)
The Atlas Computer was one of the world's first supercomputers, in use from 1962 (when it was claimed to be the most powerful computer in the world) to 1972. Atlas' capacity promoted the saying that when it went offline, half of the United Kingdom's computer capacity was lost. It is notable for being the first machine with virtual memory (at that time referred to as 'one-level store') using paging techniques; this approach quickly spread, and is now ubiquitous. Atlas was a second-generation computer, using discrete germanium transistors.
Control register
A control register is a processor register that changes or controls the general behavior of a CPU or other digital device. Common tasks performed by control registers include interrupt control, switching the addressing mode, paging control, and coprocessor control. When IBM developed a paging version of the System/360, they added 16 control registers to the design for what became the 360/67. IBM did not provide control registers on other S/360 models, but made them a standard part of System/370, although with different register and bit assignments.
Page cache
In computing, a page cache, sometimes also called disk cache, 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 to the contents of cached pages and overall performance improvements. A page cache is implemented in kernels with the paging memory management, and is mostly transparent to applications.
Mmap
mmap (« memory map ») est un appel système UNIX (norme POSIX). Il établit une projection en mémoire des fichiers ou périphériques. mmap est parfois utilisé pour la communication inter-processus. Pour cette fonctionnalité, il existe aussi l'appel système shmem. La différence entre les deux est que pour mmap, les données en mémoire ne sont pas persistantes. Certains systèmes supportent une version étendue de mmap, qui permet d'allouer de la mémoire virtuelle sans la lier à un fichier.
Page address register
A page address register (PAR) contains the physical addresses of pages currently held in the main memory of a computer system. PARs are used in order to avoid excessive use of an address table in some operating systems. A PAR may check a page's number against all entries in the PAR simultaneously, allowing it to retrieve the pages physical address quickly. A PAR is used by a single process and is only used for pages which are frequently referenced (though these pages may change as the process's behaviour changes in accordance with the principle of locality).
Copy-on-write
Le copy-on-write ou copie à l’écriture (souvent désigné par son sigle anglais COW) est une stratégie d'optimisation utilisée en programmation informatique. L'idée fondamentale : si de multiples appelants demandent des ressources initialement impossibles à distinguer, vous pouvez leur donner des pointeurs vers la même ressource. Cette fiction peut être maintenue jusqu'à ce qu'un appelant modifie sa « copie » de la ressource. À ce moment-là, une copie privée est créée. Cela évite que le changement soit visible ailleurs.
Segment de code
In computing, a code segment, also known as a text segment or simply as text, is a portion of an or the corresponding section of the program's virtual address space that contains executable instructions. The term "segment" comes from the memory segment, which is a historical approach to memory management that has been succeeded by paging. When a program is stored in an object file, the code segment is a part of this file; when the loader places a program into memory so that it may be executed, various memory regions are allocated (in particular, as pages), corresponding to both the segments in the object files and to segments only needed at run time.
Memory management (operating systems)
In operating systems, memory management is the function responsible for managing the computer's primary memory. The memory management function keeps track of the status of each memory location, either allocated or free. It determines how memory is allocated among competing processes, deciding which gets memory, when they receive it, and how much they are allowed. When memory is allocated it determines which memory locations will be assigned. It tracks when memory is freed or unallocated and updates the status.