title: Why non-blocking TCP socket would spend a lot of time in ::write() call?
body: <p>For non-blocking TCP socket, I expect <code>write()</code> or <code>read()</code> will return immediately in any case (whether <code>read()</code> can fill buffer or not, whether <code>write()</code> can send entire buffer or not).</p>
  
  <p>Is there some real world circumstances that lead to <code>write()</code> working noticeabe amount of time (milliseconds) in non-blocking mode?</p>