Deno.serve Empty Response Memory Leak

[is-jonreeves]

Version: Deno 2.1.4
OS: Windows 11 Pro

I was benchmarking Deno with K6 and noticed that some of my endpoints where using more and more memory over time. After some experimenting it seems to be only happening to those that returned an empty body:

// ❌ Empty string response = Memory increases over time
Deno.serve({ port: 3000 }, () => new Response('', { status: 200 }));

// ✅ Space character response = Memory garbage collects correctly
Deno.serve({ port: 3000 }, () => new Response(' ', { status: 200 }));

For convenience, here is an example K6 script to observe the issue:

import http from 'k6/http';

export const options = {
  vus: 50,
  duration: '5m',
};

export default function() {
  http.get('http://127.0.0.1:3000/');
}