Walter Lee, Matthew Frank, Victor Lee, Kenneth Mackenzie, and Larry Rudolph. Implications of I/O for Gang Scheduled Workloads. To Appear in 3rd Workshop on Job Scheduling Strageties for Parallel Processing , April, 1997.
(compressed postscript, 199KB)

Abstract:

This paper examines the implications of gang scheduling for general-purpose multiprocessors. The workloads in these environments include both compute-bound parallel jobs, which often require gang scheduling, and I/O-bound jobs, which require high CPU priority to achieve interactive response times. Our results indicate that an effective interactive multiprocessor scheduler must weigh both the benefits and costs of gang scheduling when deciding how to allocate resources to jobs.

This paper answers a number of questions about gang scheduling in the context of a variety of synthetic applications and SPLASH benchmarks running on the FUGU scalable multiprocessor workstation. We show that gang scheduling interferes with the performance of I/O-bound jobs, that applications do not benefit equally from gang scheduling, that most real applications can tolerate at least a small amount of scheduling skew without major performance degradation, and that messaging statistics can provide important clues to whether applications require gang scheduling. Taken together these results suggest that a multiprocessor scheduler can deliver interactive response times by dynamically monitoring and adjusting its resource allocation strategy.