title: Is 'epoll' the essential reason that Tornadoweb(or Nginx) is so fast?
body: <p><a href="http://www.tornadoweb.org" rel="noreferrer">Tornadoweb</a> and <a href="http://nginx.com" rel="noreferrer">Nginx</a> are popular web servers for the moment and many benchmarkings show that they have a better performance than Apache under certain circumstances. So my question is:</p>
  
  <p>Is 'epoll' the most essential reason that make them so fast? And what can I learn from that if I want to write a good socket server?</p>