arXiv:2510.26008v3 Announce Type: replace-cross Abstract: Large-scale machine learning workloads on the cloud suffer from silent inefficiencies, which do not trigger failures or obvious anomalies, making them hard to detect and diagnose. Existing diagnosis systems rely on guest-side instrumentation or dedicated healthy baselines. These assumptions do not hold in modern production cloud environments, where operators cannot observe inside the guest, and a healthy baseline for each setup is impractical because of system diversity. We present Unveil, a hardware-centric observability framework for detecting, identifying, and remediating silent inefficiencies using only host-visible telemetry. Unveil requires neither guest instrumentation nor application modification. It uses unsupervised learning models to detect inefficiencies and identifies known ones through a novel fingerprinting algorithm. An extensible knowledge base containing curated remediation scripts is used to correct problems without interrupting workloads when possible. We evaluate Unveil on distributed machine learning workloads, such as large language model serving, introducing less than 2% monitoring overhead. It successfully recovered from a 7% throughput loss and reduced inference latency by up to 43.48%. These results demonstrate that host-visible telemetry is sufficient for practical and continuous diagnosis of production machine learning systems.