Operating large-scale GPU training clusters (such as thousands of NVIDIA H100s or B200s interconnected via 3.2 Tbps InfiniBand) introduces an entirely new observability and operational domain. A single GPU rank stalling due to a thermal throttle or a dropped packet in a collective AllReduce ring halts all thousands of GPUs synchronously.

Without precision observability into arithmetic intensity, collective communication patterns, and hardware telemetry, engineering teams risk burning millions of dollars on sub-optimal cluster efficiency.

This module deconstructs:

  • Efficiency Metrics: Deriving theoretical peak FLOPs, Model FLOPs Utilization (MFU), and Hardware FLOPs Utilization (HFU).
  • Communication Diagnostics: Profiling NVIDIA Collective Communications Library (NCCL) ring/tree algorithms, detecting straggler ranks, and tracing InfiniBand PFC/ECN congestion.
  • Hardware Telemetry & Automated Remediation: NVIDIA Data Center GPU Manager (DCGM), XID error classification, uncorrectable PCIe/ECC errors, and automated cordon/drain pipelines.

What you will learn

  • Calculate Model FLOPs Utilization (MFU) and Hardware FLOPs Utilization (HFU) for multi-node LLM training and inference
  • Deconstruct NCCL collective communication traces: diagnose AllReduce ring/tree stalls, straggler rank latency, and RoCE/InfiniBand packet drops
  • Analyze PyTorch Profiler traces to identify kernel launch overhead, host-to-device memory transfer bottlenecks, and tensor core bubble stalls
  • Design production GPU health remediation runbooks: DCGM telemetry, thermal throttling detection, uncorrectable ECC memory errors, and automated node cordoning
STAGE TOPICS

Topics in this chapter