Performance regression on GPU

Description

Hi, recently I benchmarked the inference on GPU with AWS EC2 P3.2xlarge instance on ResNet50 pretrained model. CPU benchmark are pretty close to python, however there is a regression on GPU:

0.2.0 TF Java

p50 4.76ms
P90 6.47ms

Python (TF 2.3.1)

P50 3.24ms
P90 4.59ms

I am note sure why CPU is very close but GPU is kind of far (20% diff)

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): AWS DL AMI (Ubuntu 18.04 based)
• CUDA/cuDNN version: CUDA 10.1
• GPU model and memory: Tesla V100 16GB

Step to reproduce

You can get the Keras pretrained resnet50 model and save it to savedModel format.

Java

public class Example {
  public static void main(String[] args) {

    int ITERATION = 1000;
    String dir = "model_path";

    SavedModelBundle.Loader loader =
            SavedModelBundle.loader(dir).withTags("serve");

    SavedModelBundle bundle = loader.load();
    Session session = bundle.session();
    List<Long> timeCollector = new ArrayList<>();
    for (int i = 0; i < ITERATION; i++) {
      long start = System.nanoTime();
      forward(session);
      timeCollector.add(System.nanoTime() - start);
    }
    Collections.sort(timeCollector);
    System.out.println("P50: " + percentile(timeCollector, 50) + "ms");
    System.out.println("P90: " + percentile(timeCollector, 90) + "ms");
    System.out.println("P99: " + percentile(timeCollector, 99) + "ms");
  }

  public static double percentile(List<Long> times, int percentile) {
    int index = times.size() * percentile / 100;
    return times.get(index) / 1_000_000f;
  }

  public static void forward(Session session) {
    Session.Runner runner = session.runner();
    try(Tensor<?> tensor = Tensor.of(TFloat32.DTYPE, Shape.of(1, 224, 224, 3))) {
      runner.feed("serving_default_input_1:0", tensor);
      runner.fetch("StatefulPartitionedCall:0");
      List<Tensor<?>> result = runner.run();
    }
  }
}

python

if __name__ == "__main__":
    if len(sys.argv) != 4:
        print("usage: python3 benchmark.py <model_name> <model_dir> <num_iterations>")
        exit(1)

    model_name = sys.argv[1]
    model_path = sys.argv[2]
    iterations = int(sys.argv[3])

    print("#############################################")
    print("start testing Model: " + model_name)
    begin = time.time()

    # load model
    model = tf.saved_model.load(model_path)
    latencies = []
    for _ in range(iterations):
        inputs = tf.zeros((1, 224, 224, 3))

        start = time.time()
        result = model(inputs)
        # convert the second to mini-second
        latencies.append((time.time() - start) * 1000)
        result.numpy()

    elapsed = (time.time() - begin) * 1000
    throughput = iterations / elapsed * 1000
    p50 = np.percentile(latencies, 50)
    p90 = np.percentile(latencies, 90)
    p99 = np.percentile(latencies, 99)

    print("Model: {}".format(model_name))
    print("Iterations: {:d}".format(iterations))
    print("Throughput: {:.2f}".format(throughput))
    print("Elapsed: {:.3f} ms.".format(elapsed))
    print("P50: {:.3f} ms".format(p50))
    print("P90: {:.3f} ms".format(p90))
    print("P99: {:.3f} ms".format(p99))

从这个 issue 中的 Java 和 Python 基准测试代码片段开始，在所述的 AWS EC2 P3.2xlarge、CUDA 10.1 和 Tesla V100 环境上复现 ResNet50 比较结果。比较测量路径和 GPU 推理时间；当回归的原因已被确定，并且结果已得到修正或明确记录时，即视为完成。