The nvidia-smi (NVIDIA System Management Interface) utility is the primary tool for monitoring and managing the state of NVIDIA GPUs. When a node exhibits " jitter " or lower performance compared to its peers in a cluster, nvidia-smi provides the necessary granular data to identify the bottleneck. It reports critical metrics such as GPU utilization percentages, memory usage, and, most importantly, " Clocks Throttle Reasons. " If a GPU is running slower due to power capping, thermal issues, or a hardware error (like an uncorrectable ECC error), nvidia-smi will display this state immediately. While lspci (Option A) can confirm if the GPU is physically visible on the PCIe bus, it cannot provide any telemetry regarding its operational performance or health. iblinkinfo (Option D) is a network-level tool that only monitors InfiniBand link states. In an AI infrastructure context, nvidia-smi is the first-line diagnostic to determine if a GPU is " healthy " and operating at its intended clock speeds.