Shared memory

Material

In the context of the Computer material, the shared memory indicate a broad block of Random access memory which is reached by different Processor S in a system Multiprocessor. The problem with the shared memory is that the processors must to have an rapid access with the memory and probably have Mémoire hiding place. When a mask is updated with information who can be used by other processors, the change must be visible for the other processors, otherwise processors would work with incoherent data (see Cohérence of mask and Cohérence of memory). Protocols of maintenance of coherence can, if they function correctly, provide an access of very high efficiency with the information shared between several processors. But they can also become a bottleneck which degrades performances.

The alternatives to the shared memory are the distributed Mémoire and the shared distributed Memory. They have also problems similar. See also NUMA.

Software

In Software, the term shared memory indicates the Random access memory which is accessible by more process, where one process is an authority in the course of execution of a program. In this context, the shared memory is used to facilitate the Communication inter-process. The alternative to the memory divided is the Passage of messages. See light Process for more information.

External bonds

Shared Memory Allocation
Shared Memory Interfaces
Shared Memory Library FAQ by Márcio Serolli Pinho
Shared Memory Block FIFO Pipe Implementation Library
Article " IPC: Shared Memory" by Dave Marshall
shared memory facility from the Individual UNIX® Specification
shm_open - POSIX
shmop - documentation from SunOS 5.9
CreateSharedMemory function from Win32-SDK
Functions in PHP-API
Paper " In C++ Pooled, Shared Memory Allocator For The Standard Template Library" by Marc Ronell
Quotations from CiteSeer
Linux Shared Memory Allowance with example

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