Optimistic incremental specialization
Calton Pu, Tito Autrey, Andrew P. Black, Charles Consel, Crispin Cowan, Jon Inouye, L. Kethana, Jonathan Walpole, Kaichuang Zhang · ACM SIGOPS Operating Systems Review · 1995
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 approachisthatkernel 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 extend our specialization techniques to 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 operating systems. We also show that aggressiveuseof specialization can produce in-kernel implementations of operating system functionality with performance comparable to user-level implementations.