[Android] Support idle wakeup measurement with /proc/timer_stats

tools/perf/metrics/power.py

 # Copyright 2014 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 time
 
 from telemetry.util import process_statistic_timeline_data
 from telemetry.value import scalar
 
 from metrics import Metric
@@ skipping 52 matching lines @@
 
     self._platform.StartMonitoringPower(self._browser)
     time.sleep(measurement_time_s)
     power_results = self._platform.StopMonitoringPower()
     PowerMetric._quiescent_power_draw_mwh = (
         power_results.get('energy_consumption_mwh', 0))
 
   def Start(self, _, tab):
     self._browser = tab.browser
 
+    if self._platform.CanMeasureIdleWakeUps():
+      self._platform.StartMeasuringIdleWakeUps()
+
     if not self._platform.CanMonitorPower():
       return
 
     self._results = None
     self._StopInternal()
 
     # This line invokes top a few times, call before starting power measurement.
+    # TODO(jdduke): Move idle wakeup measurement into standalone PowerMonitor
+    # instances. Including wakeups in the "instantaneous" CPU stats object is
+    # awkward on Linux-based platforms.
     self._starting_cpu_stats = self._browser.cpu_stats
     self._platform.StartMonitoringPower(self._browser)
     self._running = True
 
   def Stop(self, _, tab):
+    if self._platform.CanMeasureIdleWakeUps():
+      self._platform.StopMeasuringIdleWakeUps()
+
     if not self._platform.CanMonitorPower():
       return
 
     self._StopInternal()
 
   def AddResults(self, _, results):
     """Add the collected power data into the results object.
 
     This function needs to be robust in the face of differing power data on
     various platforms. Therefore data existence needs to be checked when
@@ skipping 99 matching lines @@
       continue
 
     assert isinstance(cpu_stats[process_type]['IdleWakeupCount'],
         process_statistic_timeline_data.IdleWakeupTimelineData)
     idle_wakeup_delta = (cpu_stats[process_type]['IdleWakeupCount'] -
                         start_cpu_stats[process_type]['IdleWakeupCount'])
     cpu_delta[process_type] = idle_wakeup_delta.total_sum()
     total = total + cpu_delta[process_type]
   cpu_delta['Total'] = total
   return cpu_delta