Scheduling despite inexact job-size information

Motivated by the optimality of Shortest Remaining Processing Time (SRPT) for mean response time, in recent years many computer systems have used the heuristic of "favoring small jobs" in order to dramatically reduce user response times. However, rarely do computer systems have knowledge of exact remaining sizes. In this paper, we introduce the class of ε-SMART policies, which formalizes the heuristic of "favoring small jobs" in a way that includes a wide range of policies that schedule using inexact job-size information. Examples of ε-SMART policies include (i) policies that use exact size information, e.g., SRPT and PSJF, (ii) policies that use job-size estimates, and (iii) policies that use a finite number of size-based priority levels.