High memory usage for upgraded http requests

Version:
v7.7.3
Platform:
macOS/Linux
Subsystem:
net/http

I noticed that n socket connections obtained with the HTTP upgrade mechanism use a lot more memory than n socket connections obtained with a plain net server. Consider for example the following test.

net server

'use strict';

const net = require('net');

const headers = [
  'HTTP/1.1 101 Switching Protocols',
  'Connection: Upgrade',
  'Upgrade: foo',
  '',
  ''
].join('\r\n');

let count = 0;
const handler = (socket) => {
  socket.resume();
  socket.write(headers);

  if (++count === 150000) {
    gc();
    const rss = process.memoryUsage().rss;
    console.log(rss / 1024 / 1024);
  }
};

const server = net.createServer({ allowHalfOpen: true });

server.on('connection', handler);
server.listen(3000, () => console.log('listening on *:3000'));

net client

'use strict';

const net = require('net');

const headers = [
  'GET / HTTP/1.1',
  'Connection: Upgrade',
  'Upgrade: foo',
  'Host: localhost:3000',
  '',
  ''
].join('\r\n');

let i = 0;
(function createClient() {
  const socket = net.connect({
    localAddress: `127.0.0.${i % 100 + 1}`,
    port: 3000
  });

  socket.on('connect', () => {
    socket.resume();
    socket.write(headers);

    if (++i === 150000) return;

    createClient();
  });
})();

http server

'use strict';

const http = require('http');

const headers = [
  'HTTP/1.1 101 Switching Protocols',
  'Connection: Upgrade',
  'Upgrade: foo',
  '',
  ''
].join('\r\n');

let count = 0;
const handler = (req, socket, head) => {
  socket.resume();
  socket.write(headers);

  if (++count === 150000) {
    gc();
    const rss = process.memoryUsage().rss;
    console.log(rss / 1024 / 1024);
  }
};

const server = http.createServer();

server.setTimeout(0);
server.on('upgrade', handler);
server.listen(3000, () => console.log('listening on *:3000'));

http client

'use strict';

const http = require('http');

let i = 0;
(function createClient() {
  const req = http.get({
    localAddress: `127.0.0.${i % 100 + 1}`,
    port: 3000,
    headers: {
      'Connection': 'Upgrade',
      'Upgrade': 'foo'
    }
  });

  req.on('upgrade', (res, socket, head) => {
    socket.resume();

    if (++i === 150000) return;

    createClient();
  });
})();

The first (net) server uses ~295 MiB of memory while the second (http) ~525 MiB. Shouldn't they use more or less the same amount of memory?

It seems that, in part, the difference is caused by the additional event listeners. If I add

socket.removeAllListeners('drain');
socket.removeAllListeners('error');
socket.removeAllListeners('timeout');

in the upgrade event handler, memory usage drops to ~420 MiB.