A Model for Moldable Supercomputer Jobs

The performance of supercomputer schedulers is influenced by the workloads that serve as their input. Realistic workloads are therefore critical to evaluate how supercomputer schedulers perform in practice. There has been much written in the literature about rigid parallel jobs, i.e. jobs that require partitions of a fixed size to run. However the majority of the parallel jobs in production today are moldable, i.e. jobs that can execute on a variety of partition sizes. In this paper, we describe a workload model for moldable jobs, which is based on a user survey and good analytical models. Our model can serve as the basis for the development of performance-efficient strategies for selection of the job partition size, as well as the basis for enhancing supercomputer schedulers to directly accept moldable request.