This paper examinestheimplicationsofgang schedulingfor generalpurpose 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 skewwithout major performance degradation, and that messaging statistics can provide important clues to...