Profiling

js/profiling.md

Fino exposes two profiling paths: native/runtime profiling through normal Rust debug symbols, and JS CPU profile capture through fino:profiler.

JS CPU Profiles

fino:profiler starts and stops V8 CPU profile capture from JavaScript:

import { startProfiling, stopProfiling } from 'fino:profiler';
import { DiskFileSystem } from 'fino:file';

startProfiling('load');
await runWorkload();
const profile = stopProfiling('load');
await new DiskFileSystem().writeFile('profile.pb', profile);

stopProfiling() returns serialized profile bytes. Application code chooses whether to write, upload, or discard them.

Repository Profiling Fixture

The repository includes example_profile.ts for HTTP throughput profiling:

PORT=3032 cargo run -- example_profile.ts
autocannon -c 100 -d 10 http://127.0.0.1:3032/
curl http://127.0.0.1:3032/stop
go tool pprof profile.pb

Use debug builds when native symbol quality matters, and release builds when measuring throughput. Use unique ports for benchmark and profile runs so stale servers do not contaminate measurements.

The fino:profiler surface is documented in the generated API reference.