perf-host-analysis

Analyze nsys traces to detect host-side CPU overhead bottlenecks in TensorRT-LLM inference.

Updated May 23, 2026
One-click install
npx skills add https://github.com/yo-steven/skills-exploration-20260522 --skill perf-host-analysis
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: perf-host-analysis
Source: https://github.com/yo-steven/skills-exploration-20260522/tree/main/skills/TensorRT-LLM/perf-host-analysis
Command: npx skills add https://github.com/yo-steven/skills-exploration-20260522 --skill perf-host-analysis

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes scripts (resource) and references (resource) components.

What problem does it solve?

This Skill determines whether host/CPU overhead is the bottleneck in TensorRT-LLM inference by analyzing nsys traces, then isolates the specific host-side operations that regressed.

Core Features & Use Cases

  • Bottleneck detection (YES/NO): Uses GPU idle ratio, CUDA launch overhead ratio, GPU utilization, NCCL caveat, and (optionally) host-prep exposed/impact/attribution to confirm whether host overhead is actually harming throughput.
  • Root-cause analysis: Compares baseline vs target traces to quantify per-step wall-time regressions and produce an NVTX per-operation breakdown for request-management and scheduling overhead.
  • Phase-aware diagnosis: Separates context (eager) vs generation (graph replay) behavior so a regression masked in aggregate can be surfaced reliably.
  • Optional kernel-level drill-down: When NVTX indicates time inside GPU dispatch, further analyzes inter-kernel gaps, eager-vs-graph coverage, repeating patterns, and multi-rank straggler behavior.

Quick Start

Use the perf-host-analysis skill to analyze a single nsys SQLite trace file and produce a host-overhead verdict with metric evidence.

Frequently Asked Questions about perf-host-analysis

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I identify if host CPU overhead is the bottleneck in TensorRT-LLM inference?

To identify host CPU overhead in TensorRT-LLM inference, analyze nsys traces to measure GPU idle ratio, cudaLaunchKernel launch overhead, and GPU utilization. This confirms whether host-side operations are actively harming throughput.

What is the best way to diagnose performance regressions in TensorRT-LLM using nsys trace analysis?

Diagnosing TensorRT-LLM performance regressions involves comparing baseline versus target nsys traces to quantify per-step wall-time regressions. This produces an NVTX per-operation breakdown isolating scheduling and request-management overhead.

Can I separate context and generation phase behavior when profiling TensorRT-LLM?

Yes, you can separate context and generation phase behavior when profiling TensorRT-LLM. This phase-aware diagnosis isolates eager versus graph replay behavior to reliably surface regressions masked in aggregate metrics.

How do I extract iteration boundaries and compute steady-state metrics from an nsys SQLite trace?

Extracting iteration boundaries from an nsys SQLite trace relies on identifying allreduce and NVTX patterns. You then compute steady-state metrics and optionally intersect NVTX host-prep ranges with GPU idle gaps for exposed-amount attribution.

Does host overhead analysis support multi-rank straggler drill-down for TensorRT-LLM?

Host overhead analysis supports optional multi-rank straggler drill-down for TensorRT-LLM. When NVTX indicates time inside GPU dispatch, it further analyzes inter-kernel gaps, eager-vs-graph coverage, and repeating patterns across ranks.