Scheduling with global information in distributed systems

Abstract

Buffered coscheduling is a distributed scheduling methodology for time-sharing communicating processes in a distributed system, e.g., PC cluster. The principle mechanisms involved in this methodology are communication buffering and strobing. With communication buffering, communication generated by each processor is buffered and performed at the end of regular intervals (or time slices) to amortize communication and scheduling overhead. This regular communication structure is then leveraged by introducing a strobing mechanism which performs a total exchange of information at the end of each time slice. Thus, a distributed system can rely on this global information to more efficiently schedule communicating processes rather than rely on isolated or implicit information gathered from local events between processors. We describe how buffered coscheduling is implemented in the context of our SMART simulator. We then present performance measurements for two synthetic workloads and demonstrate the effectiveness of buffered coscheduling under different computational granularities, context-switch times and time-slice granularities.