ML Fleet Efficiency: Improving TPU Systems at Scale with ML Productivity Goodput

Machine learning (ML) infrastructures operating at warehouse scale present unique performance characterization challenges beyond traditional high-performance computing metrics. This paper introduces a systematic framework for analyzing ML fleet efficiency, demonstrated on Google's production TPU infrastructure comprising thousands of accelerators running diverse workloads. Our fleet-wide analysis reveals performance dependencies spanning the entire ML system stack, from hardware to model architecture, data pipelines, frameworks, compilers, and schedulers. We identify critical gaps in conventional utilization-based performance metrics and propose "ML Productivity Goodput" (MPG) to capture fleet-wide efficiency across heterogeneous ML environments. MPG decomposes efficiency into scheduling, runtime, and program components, enabling precise identification of bottlenecks at specific system layers. Applied to Google's production TPU workloads, our segmented analysis identified optimization opportunities across the stack: scheduling goodput exceeding 95% for all job sizes through careful preemption tuning, runtime improvements via framework modernization and asynchronous checkpointing, and program-level gains through compiler optimizations like communication-computation overlap. This establishes MPG as a practical methodology for managing large-scale ML computing infrastructure.