Virtual Memory vs. The File System

This paper examines the behavior of mechanisms for providing variable-size file data caches. It presents the results of running virtual-memory- and file-intensive benchmarks on the Sprite operating system [OCD88]; the benchmarks are designed to simulate real-life applications that represent the worst case for variable-size cache mechanisms. The results indicate that variable-size cache mechanisms work well when virtual-memory-and file-intensive programs are run in sequence; the cache is able to change in size in order to provide overall performance no worse than that provided by a small fixed-size cache. However, when interactive programs are run concurrently with file-intensive pro-grams, variable-size cache mechanisms perform very poorly if file pages and virtual-memory pages are treated equally. In order to guarantee good interactive response, virtu-al memory pages must be given preference over file pages