Shared memory

Unlike message queues, which offer a process-persistent messaging infrastructure, the shared memory service of IPC provides kernel-persistent memory that can be attached by an arbitrary number of processes that share common data. A shared memory infrastructure provides operation interfaces to allocate, attach, detach, and destroy shared memory regions. A process that needs access to shared data will attach or map a shared memory region into its address space; it can then access data in shared memory through the address returned by the mapping routine. This makes shared memory one of the fastest means of IPC since from a process's perspective it is akin to accessing local memory, which does not involve switch into kernel mode.

System V shared memory

Linux supports legacy SysV shared memory implementation under the IPC subsystem. Similar to SysV message queues, each shared memory region is identified by a unique IPC identifier.

Operation interfaces

The kernel provides distinct system...