title: How to read trace file(timeline) in Tensorflow
body: <p>The timeline trace file is introduced here:
  <a href="https://www.tensorflow.org/versions/r1.1/performance/xla/jit" rel="noreferrer">https://www.tensorflow.org/versions/r1.1/performance/xla/jit</a></p>
  
  <p>It seems useful for performance analyzing. But there is something I can't understand.</p>
  
  <p>1, What does "pid" stand for while there are:</p>
  
  <pre><code>    /device:GPU:0/stream:35 Compute (pid 3)
      /device:GPU:0/stream:all Compute (pid 9)
      /job:localhost/replica:0/task:0/device:CPU:0 Compute (pid 5)
  </code></pre>
  
  <p>2, A same OP can appear in different pids with absolutely different timestamp. What does that mean?</p>
  
  <p>Can anybody help me? Or is there any document about this? Thanks very much! </p>