Types of Interprocess Communication Available

Types of Interprocess Communication Available

IRIX supports IPC mechanisms of the types shown in Table 2-1.

Types of IPC and Available Implementations
Type of IPC Purpose Implementations
Shared memory A way to create a segment of memory that is mapped into the address space of two or more processes, each of which can access and alter the memory contents SVR4, IRIX
Semaphores The traditional mechanism for coordinating access to a shared resource, by which concurrent processes ensure mutually exclusive use of memory when necessary SVR4, IRIX
Locks A mechanism for mutual exclusion that is less general than the semaphore but that has less overhead IRIX
Barriers A mechanism for ensuring that all processes are ready before any of them proceed IRIX
Message Queues A set of functions by which processes can exchange messages SVR4
Sockets Virtual data connections between processes that may be in different systems BSD

Types of IPC and Available Implementations
Type of IPC	Purpose	Implementations
Shared memory	A way to create a segment of memory that is mapped into the address space of two or more processes, each of which can access and alter the memory contents	SVR4, IRIX
Semaphores	The traditional mechanism for coordinating access to a shared resource, by which concurrent processes ensure mutually exclusive use of memory when necessary	SVR4, IRIX
Locks	A mechanism for mutual exclusion that is less general than the semaphore but that has less overhead	IRIX
Barriers	A mechanism for ensuring that all processes are ready before any of them proceed	IRIX
Message Queues	A set of functions by which processes can exchange messages	SVR4
Sockets	Virtual data connections between processes that may be in different systems	BSD

These IPC features are available in different implementations:

Shared memory, semaphores, locks, and barriers are available using IRIX-unique library calls. The implementation is highly tuned, takes advantage of concurrent hardware in multiprocessors, and has a number of special features.
Shared memory, semaphores, and message queues are also provided through system function calls that are compatible with AT&T System V Release 4. This implementation is portable, but lacks some features of the IRIX IPC and is sometimes not as fast.
Socket support is compatible with BSD conventions.

Use System V IPC functions for code that must comply with the MIPS ABI, code that needs to be portable, or code that you're porting from another System V operating system. Use IRIX arena-based IPC for applications that require speed, ease of implementation, or multiprocessing ability. Socket-based IPC is necessary only for code being ported from or to a BSD system, and for network IPC.

This chapter describes the available types of System V and IRIX IPC, and provides examples of each.