title: tflite quantized inference very slow
body: <p>I am trying to convert a trained model from checkpoint file to <code>tflite</code>. I am using <code>tf.lite.LiteConverter</code>. The float conversion went fine with reasonable inference speed. But the inference speed of the <code>INT8</code> conversion is very slow. I tried to debug by feeding in a very small network. I found that inference speed for INT8 model is generally slower than float model.</p>
  
  <p>In the INT8 tflite file, I found some tensors called ReadVariableOp, which doesn't exist in TensorFlow's official mobilenet tflite model. </p>
  
  <p>I wonder what causes the slowness of INT8 inference.</p>