Neoscope: How Resilient Is My SoC to Workload Churn?

The lifetime of hardware is increasing, but the lifetime of software is not. This leads to devices that, while performant when released, have fall-off due to changing workload suitability. To ensure that performance is maintained, computer architects must begin considering the effects of evolving workloads early in the design process. The ways that workloads can change, i.e., churn, over time profoundly affect hardware's ability to maintain performance.

To better understand churn, we introduce the concepts Magnitude and Disruption, which enable how workloads change to be quantitatively described. By leveraging these terms, we present churn as a span, where the churn of a given workload can be categorized as either Minimal, Perturbing, Escalating, or Volatile. To account for how churn affects performance, we propose Neoscope, the first multi-objective pre-silicon design space exploration tool for investigating System-on-Chip (SoC) architectures that are resilient to workload churn. Neoscope uses integer linear programming and concepts from job-shop scheduling to construct near-optimal SoCs for a given workload. Unlike previous methods, Neoscope approaches (and often finds) the globally optimal SoC with a single invocation, instead of needing to parameter sweep. Neoscope is also multi-objective, i.e., it can optimize for many kinds of metrics other than absolute performance, including area, energy, cost, and carbon efficiencies. Using Neoscope, we explore near-optimal SoCs for many workload-churn configurations, and investigate how changing the objective function changes the ideal SoC. Neoscope shows that small SoCs need high levels of specialization, but that this is risky, as it increases susceptibility to churn.

• Computer systems organization → Heterogeneous (hybrid) systems.