title: General explanation of how epoll works?
body: <p>I'm doing a technical write-up on switching from a database-polling (via synchronous stored procedure call) to a message queue (via pub/sub).  I'd like to be able to explain how polling a database is vastly different and much heavier than setting up a connection to a AMQP broker and configuring a message handler.  </p>
  
  <p>Can someone maybe provide an explanation here, or point me to a good high level tutorial on how epoll works when notifying of new data becoming available on a socket?</p>