Preserving user behavior characteristics in trace-based simulation of parallel job scheduling

Evaluating the performance of a computer system requires the use of representative workloads. Therefore it is customary to use recorded job traces in simulations to evaluate the performance of proposed parallel job schedulers. We argue that this practice retains unimportant attributes of the workload, at the expense of other more important attributes. Specifically, using traces in open-system simulations retains the exact timestamps at which jobs are submitted. But in a real system these times depend on how users react to the performance of previous jobs, and it is more important to preserve the logical structure of dependencies between jobs than the specific timestamps. Using dependency information extracted from traces, we show how a simulation can preserve these dependencies. To do so we also extract user behavior, in terms of sessions and think times between the termination of one batch of jobs and the submission of a subsequent batch.