Make VR latency results compatible with perf dashboard, refactor into classes

chrome/test/vr/perf/latency/webvr_latency_test.py

Index: chrome/test/vr/perf/latency/webvr_latency_test.py
diff --git a/chrome/test/vr/perf/latency/webvr_latency_test.py b/chrome/test/vr/perf/latency/webvr_latency_test.py
new file mode 100644
index 0000000000000000000000000000000000000000..0a289a070b25e61536647716280b198f2f5248ee
--- /dev/null
+++ b/chrome/test/vr/perf/latency/webvr_latency_test.py
@@ -0,0 +1,197 @@
+# Copyright 2017 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import motopho_thread as mt
+import robot_arm as ra
+
+import json
+import glob
+import logging
+import numpy
+import os
+import re
+import subprocess
+import sys
+import time
+
+
+MOTOPHO_THREAD_TIMEOUT = 30
+
+
+def GetTtyDevices(tty_pattern, vendor_ids):
+  """Finds all devices connected to tty that match a pattern and device id.
+
+  If a serial device is connected to the computer via USB, this function
+  will check all tty devices that match tty_pattern, and return the ones
+  that have vendor identification number in the list vendor_ids.
+
+  Args:
+    tty_pattern: The search pattern, such as r'ttyACM\d+'.
+    vendor_ids: The list of 16-bit USB vendor ids, such as [0x2a03].
+
+  Returns:
+    A list of strings of tty devices, for example ['ttyACM0'].
+  """
+  product_string = 'PRODUCT='
+  sys_class_dir = '/sys/class/tty/'
+
+  tty_devices = glob.glob(sys_class_dir + '*')
+
+  matcher = re.compile('.*' + tty_pattern)
+  tty_matches = [x for x in tty_devices if matcher.search(x)]
+  tty_matches = [x[len(sys_class_dir):] for x in tty_matches]
+
+  found_devices = []
+  for match in tty_matches:
+    class_filename = sys_class_dir + match + '/device/uevent'
+    with open(class_filename, 'r') as uevent_file:
+      # Look for the desired product id in the uevent text.
+      for line in uevent_file:
+        if product_string in line:
+          ids = line[len(product_string):].split('/')
+          ids = [int(x, 16) for x in ids]
+
+          for desired_id in vendor_ids:
+            if desired_id in ids:
+              found_devices.append(match)
+
+  return found_devices
+
+
+class WebVrLatencyTest(object):
+  """Base class for all WebVR latency tests.
+
+  This is meant to be subclassed for each platform the test is run on. While
+  the latency test itself is cross-platform, the setup and teardown for
+  tests is platform-dependent.
+  """
+  def __init__(self, args):
+    self.args = args
+    self._num_samples = args.num_samples
+    self._flicker_app_url = args.url
+    assert (self._num_samples > 0),'Number of samples must be greater than 0'
+    self._device_name = 'generic_device'
+
+    # Connect to the Arduino that drives the servos
+    devices = GetTtyDevices(r'ttyACM\d+', [0x2a03, 0x2341])
+    assert (len(devices) == 1),'Found %d devices, expected 1' % len(devices)
+    self.robot_arm = ra.RobotArm(devices[0])
+
+  def RunTest(self):
+    """Runs the steps to start Chrome, measure/save latency, and clean up."""
+    self._Setup()
+    self._Run()
+    self._Teardown()
+
+  def _Setup(self):
+    """Perform any platform-specific setup."""
+    raise NotImplementedError(
+        'Platform-specific setup must be implemented in subclass')
+
+  def _Run(self):
+    """Run the latency test.
+
+    Handles the actual latency measurement, which is identical across
+    different platforms, as well as result saving.
+    """
+    # Motopho scripts use relative paths, so switch to the Motopho directory
+    os.chdir(self.args.motopho_path)
+
+    # Set up the thread that runs the Motopho script
+    motopho_thread = mt.MotophoThread(self._num_samples)
+    motopho_thread.start()
+
+    # Run multiple times so we can get an average and standard deviation
+    for _ in xrange(self._num_samples):
+      self.robot_arm.ResetPosition()
+      # Start the Motopho script
+      motopho_thread.StartIteration()
+      # Let the Motopho be stationary so the script can calculate the bias
+      time.sleep(3)
+      motopho_thread.BlockNextIteration()
+      # Move so we can measure latency
+      self.robot_arm.StartMotophoMovement()
+      if not motopho_thread.WaitForIterationEnd(MOTOPHO_THREAD_TIMEOUT):
+        # TODO(bsheedy): Look into ways to prevent Motopho from not sending any
+        # data until unplugged and replugged into the machine after a reboot.
+        logging.error('Motopho thread timeout, '
+                      'Motopho may need to be replugged.')
+      self.robot_arm.StopAllMovement()
+      time.sleep(1)
+    self._SaveResults(motopho_thread.latencies, motopho_thread.correlations)
+
+  def _Teardown(self):
+    """Performs any platform-specific teardown."""
+    raise NotImplementedError(
+        'Platform-specific setup must be implemented in subclass')
+
+  def _RunCommand(self, cmd):
+    """Runs the given cmd list and returns its output.
+
+    Prints the command's output and exits if any error occurs.
+
+    Returns:
+      A string containing the stdout and stderr of the command.
+    """
+    try:
+      return subprocess.check_output(cmd, stderr=subprocess.STDOUT)
+    except subprocess.CalledProcessError as e:
+      logging.error('Failed command output: %s', e.output)
+      raise e
+
+  def _SetChromeCommandLineFlags(self, flags):
+    raise NotImplementedError(
+        'Command-line flag setting must be implemented in subclass')
+
+  def _SaveResults(self, latencies, correlations):
+    """Saves the results to a JSON file.
+
+    Saved JSON object is compatible with Chrome perf dashboard if
+    put in as the 'chart_data' value. Also logs the raw data and its
+    average/standard deviation.
+    """
+    avg_latency = sum(latencies) / len(latencies)
+    std_latency = numpy.std(latencies)
+    avg_correlation = sum(correlations) / len(correlations)
+    std_correlation = numpy.std(correlations)
+    logging.info('Raw latencies: %s\nRaw correlations: %s\n'
+                 'Avg latency: %f +/- %f\nAvg correlation: %f +/- %f',
+                 str(latencies), str(correlations), avg_latency, std_latency,
+                 avg_correlation, std_correlation)
+
+    if not (self.args.output_dir and os.path.isdir(self.args.output_dir)):
+      logging.warning('No output directory set, not saving results to file')
+      return
+
+    results = {
+      'format_version': '1.0',
+      'benchmark_name': 'webvr_latency',
+      'benchmark_description': 'Measures the motion-to-photon latency of WebVR',
+      'charts': {
+        'correlation': {
+          'summary': {
+            'improvement_direction': 'up',
+            'name': 'correlation',
+            'std': std_correlation,
+            'type': 'list_of_scalar_values',
+            'units': '',
+            'values': correlations,
+          },
+        },
+        'latency': {
+          'summary': {
+            'improvement_direction': 'down',
+            'name': 'latency',
+            'std': std_latency,
+            'type': 'list_of_scalar_values',
+            'units': 'ms',
+            'values': latencies,
+          },
+        }
+      }
+    }
+
+    with file(os.path.join(self.args.output_dir,
+                           self.args.results_file), 'w') as outfile:
+      json.dump(results, outfile)