Abstract

Shared-memory multiprocessors (SMPs) are being exten-sively used as general-purpose servers. The tight coupling of multiple processors, memory, and I/O provides enormous computing power in a single system, and enables the effi-cient sharing of these resources. The operating systems for these machines (UNIX or Win-dows NT) provide very few controls for sharing the resources of the system among the active tasks or users. This unconstrained sharing model is a serious limitation for a server because the load placed by one user can adversely affect other users ’ performance in an unpredictable manner. We show that this lack of isolation is caused by the resource allocation scheme (or lack thereof) carried over from single-user workstations. Multi-user multiprocessor systems require more sophisticated resource management, and we show how the proposed “performance isolation ” scheme can address the current weaknesses of these systems. We have implemented performance isolation in the Silicon Graphics IRIX operating system for three important system resources: CPU time, memory, and disk bandwidth. Running a number of workloads we show that our proposed scheme is success-ful at providing workstation-like isolation under heavy load, SMP-like latency under light load, and SMP-like throughput in all cases. 1.

Citations