message: Add logging for extreme values of the infeed queue.
  Reviewers: davidn, #tensorflow
diff: @@ -460,9 +460,13 @@ std::function<void()> PoplarExecutor::CreateInfeedIOThreadFunction(
  // only need to check if the first queue is full to know whether all the
  // queues are full.
  if (infeed_dataset_iterator->tensor_queues[0][0]->IsFull()) {
  + VLOG(1) << "Infeed queue is full.";
  continue;
  }
  + const bool was_empty =
  + infeed_dataset_iterator->tensor_queues[0][0]->IsEmpty();
  +
  bool end_of_sequence = false;
  std::vector<tensorflow::Tensor> outputs;
  auto status = infeed_dataset_iterator->iterator->GetNext(
  @@ -505,6 +509,10 @@ std::function<void()> PoplarExecutor::CreateInfeedIOThreadFunction(
  queue->AdvanceWritePosition();
  }
  }
  +
  + if (was_empty) {
  + VLOG(1) << "Infeed queue is empty.";
  + }
  } else {
  infeed_thread_cancelled_ = true;
  LOG(INFO)
  