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

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

Index: chrome/test/vr/perf/latency/motopho_thread.py
diff --git a/chrome/test/vr/perf/latency/motopho_thread.py b/chrome/test/vr/perf/latency/motopho_thread.py
new file mode 100644
index 0000000000000000000000000000000000000000..aca45614e432af1c90d83f38fa79ff85c6a0cf70
--- /dev/null
+++ b/chrome/test/vr/perf/latency/motopho_thread.py
@@ -0,0 +1,83 @@
+# 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 logging
+import subprocess
+import threading
+
+
+class MotophoThread(threading.Thread):
+  """Handles the running of the Motopho script and extracting results."""
+  def __init__(self, num_samples):
+    threading.Thread.__init__(self)
+    self._num_samples = num_samples
+    self._latencies = []
+    self._correlations = []
+    # Threads can't be restarted, so in order to gather multiple samples, we
+    # need to either re-create the thread for every iteration or use a loop
+    # and locks in a single thread -> use the latter solution
+    self._start_lock = threading.Event()
+    self._finish_lock = threading.Event()
+    self.BlockNextIteration()
+
+  def run(self):
+    for _ in xrange(self._num_samples):
+      self._WaitForIterationStart()
+      self._ResetEndLock()
+      motopho_output = ""
+      try:
+        motopho_output = subprocess.check_output(["./motophopro_nograph"],
+                                                 stderr=subprocess.STDOUT)
+      except subprocess.CalledProcessError as e:
+        logging.error('Failed to run Motopho script: %s', e.output)
+        raise e
+
+      if "FAIL" in motopho_output:
+        logging.error('Failed to get latency, logging raw output: %s',
+                      motopho_output)
+        raise RuntimeError('Failed to get latency - correlation likely too low')
+
+      current_num_samples = len(self._latencies)
+      for line in motopho_output.split("\n"):
+        if 'Motion-to-photon latency:' in line:
+          self._latencies.append(float(line.split(" ")[-2]))
+        if 'Max correlation is' in line:
+          self._correlations.append(float(line.split(' ')[-1]))
+        if (len(self._latencies) > current_num_samples and
+            len(self._correlations) > current_num_samples):
+          break;
+      self._EndIteration()
+
+  def _WaitForIterationStart(self):
+    self._start_lock.wait()
+
+  def StartIteration(self):
+    """Tells the thread to start its next test iteration."""
+    self._start_lock.set()
+
+  def BlockNextIteration(self):
+    """Blocks the thread from starting the next iteration without a signal."""
+    self._start_lock.clear()
+
+  def _EndIteration(self):
+    self._finish_lock.set()
+
+  def _ResetEndLock(self):
+    self._finish_lock.clear()
+
+  def WaitForIterationEnd(self, timeout):
+    """Waits until the thread says it's finished or times out.
+
+    Returns:
+      Whether the iteration ended within the given timeout
+    """
+    return self._finish_lock.wait(timeout)
+
+  @property
+  def latencies(self):
+    return self._latencies
+
+  @property
+  def correlations(self):
+    return self._correlations