Operating system support for flexible coherence in distributed object systems

COMMOS is an operating system architecture developed to support shared persistent objects in distributed systems. This paper describes its support for flexible coherence. The approach is based on a microkernel, typed memory objects and integrated coherence control. A microkernel architecture is used to make it easier to support multiple coherence protocols and to add new protocols. Memory objects are typed and applications can choose the most suitable protocols for different types of object to avoid protocol mismatch. Low-level coherence control is integrated with high-level concurrency control so that system-wide object coherence and synchronisation are realised without severely impacting the system performance