Migrating to Processor Sharing

This paper describes experiences gained while adding processor sharing capabilities to the ARCADE distributed system. The goal of a processor sharing facility (PSF) is to allow busy users to take advantage of cycles available on idle processors, which are typically plentiful in a network of individually-owned machines. Several researchers have reported positive experiences with implementing a PSF in their own distributed systems. Encouraged by these reports, we embarked on a project to add this capability to ARCADE. Early on we realized that the original ARCADE architecture lacked some of the basic mechanisms required by a PSF. Thus, we needed to extend and modify ARCADE; this paper describes our experiences to date in doing so. In addition, we present some performance measurements and note lessons we have learned while making extensive changes to our architecture and prototype implementation.