cpu-profile-analysis

Parse the JSON to build a node map from the nodes array, then walk the samples array to compute self-time per function using timeDeltas. Sort functions by self-time descending to find the top CPU consumers and group samples into time buckets to identify activity regions.

A .cpuprofile contains only V8 sampling profiler data (nodes, samples, timeDeltas). A Trace-*.json uses the Chrome Trace Event Format with a traceEvents array covering CPU samples, layout, paint, GC, user timing marks, and multi-process data from Renderer, Browser, and GPU processes.

V8 cannot create strings larger than roughly 512MB, so readFileSync with utf8 encoding fails on huge profiles. Read the file as a raw Buffer instead, scan for JSON key boundaries by bytes, and parse small sub-buffer sections individually.

Filter traceEvents for entries named RunTask with phase X and dur greater than 50000 microseconds on the CrRendererMain thread. Sort by duration descending to surface the tasks blocking the main thread longest.

Yes. Trace files embed the full CPU profile as Profile and ProfileChunk events under the disabled-by-default-v8.cpu_profiler category. Merge the nodes, samples, and timeDeltas from all chunks sharing the same profile id, then analyze them like a standard .cpuprofile.