Telemetry: Implement idle wakeups counting on Android.

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 metrics import Metric
 from telemetry.core.platform import process_statistic_timeline_data
 from telemetry.value import scalar
 
@@ skipping 51 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.
     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 63 matching lines @@
     cstate_percent = whole_package_utilization.get('cstate_residency_percent')
     if cstate_percent is not None:
       for state, percent in cstate_percent.iteritems():
         results.AddValue(scalar.ScalarValue(
             results.current_page, 'cpu_cstate_%s_residency_percent' % state,
             '%', percent, important=False))
 
     self._results = None
 
 def _SubtractCpuStats(cpu_stats, start_cpu_stats):
   """Computes number of idle wakeups that occurred over measurement period.

[jdduke (slow), 2015/07/09 21:00:19]

Hmm, the way /proc/timer_stats collection works I'm not sure we can subtract the
before/after values (as the values are really only valid within the scope of
enabling collection).

Perhaps we could have |StopMeasuringIdleWakeUps| return the total wakeups scoped
by |StartMeasuringIdleWakeups|? So Mac would do subtraction, and Android (Linux)
would just return the raw data from /proc/timer_stats? If we do that, I wonder
if it makes sense (or would be less confusing) to remove IdleWakeupCount as a
member of CPU stats.

 
   Each of the two cpu_stats arguments is a dict as returned by the
   Browser.cpu_stats call.
 
   Returns:
     A dict of process type names (Browser, Renderer, etc.) to idle wakeup count
     over the period recorded by the input.
   """
   cpu_delta = {}
   total = 0
   for process_type in cpu_stats:
     assert process_type in start_cpu_stats, 'Mismatching process types'
     # Skip any process_types that are empty.
     if (not cpu_stats[process_type]) or (not start_cpu_stats[process_type]):
       continue
     # Skip if IdleWakeupCount is not present.
     if (('IdleWakeupCount' not in cpu_stats[process_type]) or
         ('IdleWakeupCount' not in start_cpu_stats[process_type])):
       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