Implementation and Performance of Integrated Application-Controlled File Caching, Prefetching and Disk Scheduling

As the performance gap between disks and microprocessors continues to increase, effective utilization of the file cache becomes increasingly important. Application-controlled file caching and prefetching can apply application specific knowledge to improve file cache management. However, supporting application-controlled file caching and prefetching is nontrivial because caching and prefetching need to be integrated carefully, and the kernel needs to allocate cache blocks among processes appropriately. This paper presents the design, implementation and performance of a file system that integrates application-controlled caching, prefetching and disk scheduling. We use a two-level cache management strategy. The kernel uses the LRU-SP (Least-Recently-Used with Swapping and Placeholders) policy to allocate blocks to processes, and each process integrates application-specific caching and prefetching based on the controlledaggressive policy, an algorithm previously shown in a theoretical sen..