The Linux Programming Interface

48SYSTEM V SHARED MEMORY

This chapter describes System V shared memory. Shared memory allows two or more processes to share the same region (usually referred to as a segment) of physical memory. Since a shared memory segment becomes part of a process’s user-space memory, no kernel intervention is required for IPC. All that is required is that one process copies data into the shared memory; that data is immediately available to all other processes sharing the same segment. This provides fast IPC by comparison with techniques such as pipes or message queues, where the sending process copies data from a buffer in user space into kernel memory and the receiving process copies in the reverse direction. (Each process also incurs the overhead of a system ...