Не уверен что в ОС.
Хотя, вот мужик добился лучших показателей (для выборов в штатах)
Вобщем ясно, что надо копать и твикать. Кстати, в статье есть наводки, которые завтра испытаю.

Clearly, this research became something of a rabbit’s hole for me. Since the US Elections Committee wasn’t particularly concerned with my stress testing results, election night came and went before I solved the performance problems. I’m happy to report that our Node.js application performed just fine–between 10,000 WebSockets and 10,000 long-polling connections, we hit a manageable client distribution that was somewhere between “all WebSocket” and “all long-polling”.