title: Upper limit of file descriptor in Linux
body: <p>what is the upper limit of file-descriptor that can be used in any Linux system (specifically ubuntu 10.04)? </p>
  
  <p>I am using Ubuntu 10.04 (64-bit) and my CPU architecture for server is x86_64 and for client it is i686. Right now I had increased my fd-limit to 400000.</p>
  
  <ul>
  <li>What can be the possible side-effects of using large no. of file descriptors?</li>
  <li>How can I know about the no. file-descriptor that is used by any process?</li>
  </ul>
  
  <p>Thnx</p>