Advanced Search

Log In | Not a Member? Contact ADC

Mach Overview

The fundamental services and primitives of the Mac OS X kernel are based on Mach 3.0. Apple has modified and extended Mach to better meet Mac OS X functional and performance goals.

Mach 3.0 was originally conceived as a simple, extensible, communications microkernel. It is capable of running as a stand–alone kernel, with other traditional operating-system services such as I/O, file systems, and networking stacks running as user-mode servers.

However, in Mac OS X, Mach is linked with other kernel components into a single kernel address space. This is primarily for performance; it is much faster to make a direct call between linked components than it is to send messages or do remote procedure calls (RPC) between separate tasks. This modular structure results in a more robust and extensible system than a monolithic kernel would allow, without the performance penalty of a pure microkernel.

Thus in Mac OS X, Mach is not primarily a communication hub between clients and servers. Instead, its value consists of its abstractions, its extensibility, and its flexibility. In particular, Mach provides

• object-based APIs with communication channels (for example, ports) as object references

• highly parallel execution, including preemptively scheduled threads and support for SMP

• a flexible scheduling framework, with support for real-time usage

• a complete set of IPC primitives, including messaging, RPC, synchronization, and notification

• support for large virtual address spaces, shared memory regions, and memory objects backed by persistent store

• proven extensibility and portability, for example across instruction set architectures and in distributed environments

• security and resource management as a fundamental principle of design; all resources are virtualized

Contents:

Mach Kernel Abstractions
Tasks and Threads
Ports, Port Rights, Port Sets, and Port Namespaces
Memory Management
Interprocess Communication (IPC)
Time Management

Did this document help you? Yes: Tell us what works for you. It’s good, but: Report typos, inaccuracies, and so forth. It wasn’t helpful: Tell us what would have helped.

	Get information on Apple products. Visit the Apple Store online or at retail locations. 1-800-MY-APPLE Copyright © 2007 Apple Inc. All rights reserved. | Terms of use | Privacy Notice