1. Mach Kernel
Kris Ambrose
Kris Ambrose 2003

2. Overview
A research project at Carnegie Mellon University (CMU) from 1985 to 1994.
Considered to be the next great operating system
Designed to incorporate many new OS technologies
Microkernel
Multiprocessing
Interprocess Communication (IPC)
Distributed Operation
Portable across heterogeneous hardware
And still maintain BSD Unix compatible
Kris Ambrose 2003

3. Mach Kernel Abstractions
Task – a basic unit of resource allocation that must contain an address space and may contain port rights and threads.
Thread – a basic unit of CPU utilization that belongs to a task and uses the task’s resource allocation.
Port – a communication channel that the kernel protects, allows for all parts of the kernel and tasks to pass messages back and forth.
Message – a typed collection of data objects that may be actual data, port rights, or a pointer out-of-line-data.
Memory Object – a basic unit of memory used within the kernel and the a task may access it by mapping parts or all of it into its address space.
Kris Ambrose 2003

4. Mach’s Abstractions Silberschatz, Galvin, Gagne
(2003) Appendix B: Mach
Kris Ambrose 2003

5. Mach as a Microkernel Minimizes Kernel Operations
Task and Thread Management
IPC
Virtual Memory
Acts as a Virtual Machine
Parts are Modular
Kris Ambrose 2003

6. Structure of Mach
Billard (2001): Mach Design
Kris Ambrose 2003

7. Multiprocessing in Mach
Threads are scheduled not tasks
Threads are CPU independent
Preemptive Scheduling done with a Priority Queue
Quantum is based on Number of CPUs and Threads
Threads to run across many processors
Global and Local Run Queues
Kris Ambrose 2003

8. Interprocess Communication
Tasks and Threads pass messages
Ports accept messages
Port rights are assigned for protection
Tasks may create Port Sets
Large Messages use Copy-On-Write
Kris Ambrose 2003

9. Distributed Operation and Portability
Each Server Contains a different Module
Fast and Secure reload
Multiple CPUs may be used for different Modules
Runs across different Architectures
Kris Ambrose 2003

10. Unix Compatibility Allows for Unix System calls Mach needs Unix
Acts as a Virtual Machine
Kris Ambrose 2003

11. Today and Beyond
Many of the Operating Systems today use the ideas of Mach
QNX
Hurd
Mach 4
Real-Time Mach
Some Actually Use the Mach/FreeBSD
NeXT
Mac OS X (based on NeXT)
IBM OS/2 for the RS6000 based machines
The Open Software Foundation (OSF) is still doing further research and development
Kris Ambrose 2003

12. Summary Originally CMU and OSF Research Project Major Accomplishments
Microkernel
Multiprocessing
Interprocess Communication
Distributed Operations
Portable
BSD Unix Compatible
Concepts still used
Kris Ambrose 2003

13. The End
Kris Ambrose 2003