Analyze Performance Profiles

Analyze .cpuprofile files (V8 sampling profiler) and DevTools trace files (Trace-*.json, Chrome Trace Event Format) to find performance bottlenecks, compare code paths, and understand timing.

When to Use

• User provides a .cpuprofile or Trace-*.json file and wants to understand performance
• Investigating why one code path is slower than another
• Finding what functions consume the most time
• Comparing "before/after" or "old/new" implementations in a single profile
• Investigating layout thrashing, long tasks, or rendering bottlenecks (trace files)
• Analyzing VS Code user timing marks like code/didResolveTextFileEditorModel (trace files)
• Understanding multi-process behavior (Browser, Renderer, GPU processes in trace files)

Detecting File Type

• .cpuprofile: Top-level JSON with nodes, samples, timeDeltas keys. Created by the VS Code profiler.
• Trace-*.json: Top-level JSON with traceEvents array (and optional metadata). Created by Chrome/Electron DevTools (Performance tab). These are richer than .cpuprofile -- they contain CPU samples, layout/paint events, user timing marks, GC events, input events, and multi-process data.

Key Concepts