Effects of Reconfiguration on Performance in Configurable Operating Systems: Practical Predictability Strategies?

Critical systems must be configured to meet changing functionality, time-criticality and fault-tolerance needs. Configurations may be performed statically at operating system build or boot -time. Dynamic configurations are also possible during run-time, when the operating system is loaded and running. For example, operating sytem kernel modules, operating system components, middleware and application programs may all be configured statically or dynamically. Operating systems may be configured to scale from ROMable versions to full-fledged multiprocessor clusters, which we term, the horizontal configurability feature. In addition, to address different types of applications, operating systems may be configured with enhanced or reduced functionality, which we term the vertical configurability feature. Finally, when such configurations are performed, higher level operating system components, middleware, and other Commercial Off-The-Shelf (COTS) software products expect to experience the gains derived from such configurations in terms of enhanced performance or predictability