A Dynamically Reconfigurable and Extensible Operating System

Alistair C. Veitch (Ph.D. thesis)

Abstract:

Operating systems are constantly getting more complex in the functionality they support, due to the increasing demands made by modern hardware and software innovations. Basing the kernel design on cooperating and modular services incorportating a flexible communications infrastructure with runtime binding makes the operating system dynamically configurable and extensible. These features aid in the management of system complexity, while also resulting in several software engineering and performance benefits. Configurability gives the operating system designer and implementor the freedom to build a large number of components, which can be composed into different configurations depending upon the final system requirements. System components can be built and debugged in a user address space, and then transparently migrated into the kernel address space for performance once they have been demonstrated correct. This removes one of the major obstacles to developing kernel services, that of the necessity to reboot the system after each change to the service code. The system administrator can also reconfigure the system, providing similar advantages, and allowing dynamic system upgrades to be made, reducing system downtime. Extensibility lets new functionality be integrated into the operating system. This can be done on an application specific basis. This enables the development of in-kernel applications in cases where high performance is required, such as for dedicated file servers. It is also possible for applications to interpose specialised kernel services, allowing them to dramatically increase their performance and aggregate system throughput when the default system policies are ill-matched to their behaviour. The Kea operating system has been designed and implemented to be dynamically configurable and extensible. The design of the system features that make these features possible are described. Experimental results are shown that demonstrate that Kea offers comparable performance to a traditional operating system on the same hardware, and that extensibility can be used to increase performance for selected applications.

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Last modified: Tue Jul 10 21:36:53 PDT 2001 by Alistair Veitch (aveitch@hpl.hp.com)