title: How to measure TCP back pressure?
body: <p>I am trying to investigate a performance issue with code that publishes data to a server over a TCP socket.  One hypothesis is that the publisher is experiencing back pressure at the socket level.  Is there a way to get a back-pressure metric from the operating system?</p>
  <p>I'm sure the answer is specific to the operating system.  In my case, I am using Linux.</p>