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

tools/telemetry/telemetry/internal/platform/android_platform_backend.py

Index: tools/telemetry/telemetry/internal/platform/android_platform_backend.py
diff --git a/tools/telemetry/telemetry/internal/platform/android_platform_backend.py b/tools/telemetry/telemetry/internal/platform/android_platform_backend.py
index dc93b3062b0beea845ab095754244023b6c78d81..eaeb52e6969d55b66e41255ee010d7c1e3447021 100644
--- a/tools/telemetry/telemetry/internal/platform/android_platform_backend.py
+++ b/tools/telemetry/telemetry/internal/platform/android_platform_backend.py
@@ -27,6 +27,7 @@ from telemetry.internal.platform.power_monitor import power_monitor_controller
 from telemetry.internal.platform.profiler import android_prebuilt_profiler_helper
 from telemetry.internal.util import exception_formatter
 from telemetry.internal.util import external_modules
+from telemetry.util import process_statistic_timeline_data
 
 psutil = external_modules.ImportOptionalModule('psutil')
 util.AddDirToPythonPath(util.GetChromiumSrcDir(),
@@ -264,7 +265,11 @@ class AndroidPlatformBackend(
     if not self._can_access_protected_file_contents:
       logging.warning('CPU stats cannot be retrieved on non-rooted device.')
       return {}
-    return super(AndroidPlatformBackend, self).GetCpuStats(pid)
+    results = super(AndroidPlatformBackend, self).GetCpuStats(pid)
+    idle_wakeup_count = self._GetIdleWakeupCount(pid)
+    if idle_wakeup_count:
+      results.update({'IdleWakeupCount': idle_wakeup_count})
+    return results
 
   def GetCpuTimestamp(self):
     if not self._can_access_protected_file_contents:
@@ -432,6 +437,9 @@ class AndroidPlatformBackend(
   def CanMonitorPower(self):
     return self._power_monitor.CanMonitorPower()
 
+  def CanMeasureIdleWakeUps(self):
+    return True
+
   def StartMonitoringPower(self, browser):
     self._power_monitor.StartMonitoringPower(browser)
 
@@ -454,9 +462,14 @@ class AndroidPlatformBackend(
     return self._device.ReadFile(fname, as_root=True)
 
   def GetPsOutput(self, columns, pid=None):
+    return self._GetPsOutput(columns=columns, pid=pid)
+
+  def _GetPsOutput(self, columns, list_threads=False, pid=None):
     assert columns == ['pid', 'name'] or columns == ['pid'], \
         'Only know how to return pid and name. Requested: ' + columns
     command = 'ps'
+    if list_threads:
+      command += ' -t'
     if pid:
       command += ' -p %d' % pid
     ps = self._device.RunShellCommand(command, large_output=True)[1:]
@@ -699,6 +712,42 @@ class AndroidPlatformBackend(
     """
     return '/data/data/%s/' % package
 
+
+  def _GetIdleWakeupCount(self, pid):
+    """Find the given pid in the timer_stats and sum up the wake-up count.
+
+    Each row is in the form of: wake_up_count, pid process_name reason
+    Due to possibly multiple reasons, a given pid can appear in multiple rows.
+    """
+    contents = self.GetFileContents('/proc/timer_stats')
+    if not contents:
+      return None
+    count = 0
+    split_lines = contents.splitlines()
+    matching_pids = []
+    # The pid listed by timer_stats is the *kernel* pid (potentially different
+    # for each thread), which may differ from the provided process pid. Use ps
+    # to map each thread pid back to the proper process pid (tgid).
+    for matching_pid in self._GetPsOutput(['pid'], list_threads=True,
+                                          pid=int(pid)):
+      matching_pids.append(matching_pid[0])
+    for line in split_lines[:-1]:
+      line_split = line.split(',', 1)
+      if len(line_split) < 2:
+        continue
+      count_str, rest_str = line_split
+      current_pid = rest_str.strip().split(' ')[0]
+      if current_pid == pid or current_pid in matching_pids:
+        # The "D" suffix on the count indicates a "deferrable" timer.
+        count += int(count_str.strip().rstrip('D'))
+    return process_statistic_timeline_data.IdleWakeupTimelineData(pid, count)
+
+  def _EnableTimerStatsCollection(self, enable):
+    """Writes to /proc/timer_stats to start/stop measuring process wakeups."""
+    parameter = 1 if enable else 0
+    cmd = 'echo %d > /proc/timer_stats' % parameter
+    self._device.RunShellCommand(cmd, as_root=True)
+
   def SetDebugApp(self, package):
     """Set application to debugging.