perMessageDeflate feature questions

[darrachequesne]

Hi!

• should the perMessageDeflate really be enabled by default? I saw it was set to false as default by this commit f7ef85c (but then quickly overriden by 71ff077). I think it may be a bit disturbing when migrating from older version (or for newcomers), as it has some (pretty important) impact on performance (as seen here The sharp decline of the speed of transmission in the latest versions #454).
• how can one pass custom options to PerMessageDeflate object (like memLevel or maxWindowBits, to adjust the rate compression performance / memory consumption)? From https://github.com/websockets/ws/blob/master/lib/WebSocketServer.js#L490

  var options = this.options.perMessageDeflate;
  if (options && offer[PerMessageDeflate.extensionName]) {
    var perMessageDeflate = new PerMessageDeflate(options !== true ? options : {}, true);

[Edit] for the 2nd question, I should have read the docs here https://github.com/websockets/ws/blob/master/doc/ws.md

[darrachequesne]

Since the feature seems now stable (through #595 and #608), I'll close this! Sorry for the noise 👼