Optimistic Incremental Specialization: Streamlining a Commercial Operating System

Conventional operating system code is written to deal with all possible system states, and performs considerable interpretation to determine the current system state before taking action. A consequence of this approach is that kernel calls which perform little actual work take a long time to execute. To address this problem, we use specialized operating system code that reduces interpretation for common cases, but still behaves correctly in the fully general case. We describe how specialized operating system code can be generated and bound incrementally as the information on which it depends becomes available. We extendour specialization techniquesto include the notion of optimistic incremental specialization: a technique for generating specialized kernel code optimistically for system states that are likely to occur, but not certain. The ideas outlined in this paper allow the conventional kernel design tenet of "optimizing for the common case" to be extended to the domain of adaptive..