Experience with the development of a microkernel-based, multiserver operating system

During the first half of the 1990s, IBM developed a set of operating system products called Workplace OS that was based on the Mach 3.0 microkernel and Taligent's object-oriented TalOS. These products were intended to be scalable, portable and capable of concurrently running multiple operating system personalities while sharing as much code as possible. The operating system personalities were constructed out of a set of user-level personality and personality-neutral servers and libraries. While we made a number of important changes to Mach 3.0, we maintained its fundamentals and the multi-server design throughout our project. In evaluating the resulting system, a number of problems are apparent. There is no good way to factor multiple existing systems into a set of functional servers without making them excessively large and complex. In addition, the message-passing nature of the microkernel turns out to be a poor match for the characteristics of modern processors, causing performance problems. Finally, the use of fine-grained objects complicated the design and further reduced the performance of the system. Based on this experience, I believe that more modest, more targeted operating systems consume fewer resources, offer better performance and can provide the desired semantics with fewer compromises.