Opportunity Scheduling: An Unfair CPU Scheduler for UNICOS

: Fair Share is the standard scheduling algorithm used for political resource control on large, multi-user UNIX systems. Promising equity, Fair Share has instead delivered frustration to its Los Alamos UNICOS users, who perceive misallocations of interactive response within a system of unreasonable complexity. This paper reviews the design of the Kay/Lauder Fair Share system, as well as its Cray UNICOS implementation, and concludes that the underlying model is inappropriate for interactive control. A new resource manager, Opportunity Scheduling, is then presented. Salient features of the new scheduler include: (1) direct management of interactivity (or "computing opportunity"), (2) job prioritization within resource groups, (3) cooperative memory scheduling, and (4) a simple, user-oriented interface. The paper then contrasts Opportunity Scheduling with the batch system employed at Los Alamos, where throughput and cycle allocation, rather than computing opportunity, are paramount consid..