一句话:提出非侵入式跨层根因分析框架 TELLER,用结构化 trace 表示与多模态模型定位 LLM 推理异常步骤并生成解释。
LLM 推理已成为持续运行的在线服务,单次请求横跨推理引擎、Python/C++ 后端、CUDA API、GPU kernel 与分布式通信,现有 profiler 只暴露原始时间线、日志诊断缺乏跨层语义与请求级结构,根因分析困难。TELLER 不修改模型二进制即可采集 NVTX/CUPTI trace 与服务日志,重建每请求调用链树并对齐日志;提出依赖感知因果上下文切片与 Trace Pair Encoding 分词器,将切片压缩为带父节点、深度、时长属性的结构化 token 序列,再以数值候选定位结合多模态根因模型联合预测异常步骤、定位可疑算子并生成自然语言解释。多节点 GPU 负载上,中等词表在压缩每步 trace 80% 以上的同时取得横纵向视图最佳性能,过度压缩则显著降低诊断质量。
Large language model (LLM) inference has evolved from an offline workload into a continuously operated software service, yet root-cause analysis remains difficult because a single request spans the inference engine, Python/C++ backend, host CUDA APIs, GPU kernels, and distributed communication. Existing profilers expose raw timelines, while log-based diagnosis often misses cross-layer execution semantics and request-level structure. We present TELLER, a non-intrusive trace- and log-aware LLM inference root-cause analysis framework. TELLER first collects NVTX/CUPTI traces and service logs without modifying model binaries, then reconstructs per-request call-chain trees and aligns log lines with the corresponding execution steps. We introduce a dependency-aware causal-context slice that preserves parent-child structure, temporal order, and communication relations, and a Trace Pair Encoding (TPE) tokenizer that compresses such slices into compact structural token sequences with parent, depth, and duration attributes. On top of these representations, TELLER combines numeric candidate localization with a multimodal root-cause model that jointly predicts abnormal steps, localizes suspicious operators, and generates natural-language explanations. Experiments on multi-node GPU inference workloads show a clear compression-accuracy trade-off: a moderate TPE vocabulary reduces per-step trace length by more than 80% while achieving the best overall performance on both horizontal (cross-node communication) and vertical (within-node execution stack) views, whereas more aggressive compression substantially degrades diagnosis quality. Further analyses under low-fault priors, strengthened baselines, modality ablations, explanation-quality checks, and tracing overhead show that TELLER provides a practical triage and evidence-localization substrate for LLM inference RCA.