Characterizing Machine Learning-Based Runtime Prefetcher Selection

Modern computer designs support composite prefetching, where multiple prefetcher components are used to target different memory access patterns. However, multiple prefetchers competing for resources can sometimes hurt performance, especially in many-core systems where cache and other resources are limited. Recent work has proposed mitigating this issue by selectively enabling and disabling prefetcher components at runtime. Formulating the problem with machine learning (ML) methods is promising, but efficient and effective solutions in terms of cost and performance are not well understood. This work studies fundamental characteristics of the composite prefetcher selection problem through the lens of ML to inform future prefetcher selection designs. We show that prefetcher decisions do not have significant temporal dependencies, that a phase-based rather than sample-based definition of ground truth yields patterns that are easier to learn, and that prefetcher selection can be formulated as a workload-agnostic problem requiring little to no training at runtime.