Upstreaming latest build/android changes

build/android/pylib/perf_tests_helper.py

 # Copyright (c) 2012 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 re
 
 import android_commands
+import math
 
 # Valid values of result type.
 RESULT_TYPES = {'unimportant': 'RESULT ',
                 'default': '*RESULT ',
                 'informational': ''}
 
 
 def _EscapePerfResult(s):
   """Escapes |s| for use in a perf result."""
   # Colons (:) and equal signs (=) are not allowed, and we chose an arbitrary
@@ skipping 21 matching lines @@
 
     Returns:
       String of the formated perf result.
   """
   assert result_type in RESULT_TYPES, 'result type: %s is invalid' % result_type
 
   assert isinstance(values, list)
   assert len(values)
   assert '/' not in measurement
   avg = None
+  sd = None
   if len(values) > 1:
     try:
       value = '[%s]' % ','.join([str(v) for v in values])
       avg = sum([float(v) for v in values]) / len(values)
+      sqdiffs = [(float(v) - avg) ** 2 for v in values]
+      variance = sum(sqdiffs) / (len(values) - 1)
+      sd = math.sqrt(variance)
     except ValueError:
       value = ", ".join(values)
   else:
     value = values[0]
 
   trace_name = _EscapePerfResult(trace)
   output = '%s%s: %s%s%s %s' % (
     RESULT_TYPES[result_type],
     _EscapePerfResult(measurement),
     trace_name,
     # Do not show equal sign if the trace is empty. Usually it happens when
     # measurement is enough clear to describe the result.
     '= ' if trace_name else '',
     value,
     units)
   if avg:
     output += '\nAvg %s: %f%s' % (measurement, avg, units)
+  if sd:
+    output += '\nSd  %s: %f%s' % (measurement, sd, units)
   if print_to_stdout:
     print output
   return output
 
 
 class PerfTestSetup(object):
   """Provides methods for setting up a device for perf testing."""
   _DROP_CACHES = '/proc/sys/vm/drop_caches'
   _SCALING_GOVERNOR = '/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor'
 
   def __init__(self, adb):
     self._adb = adb
     num_cpus = self._adb.GetFileContents('/sys/devices/system/cpu/online',
                                          log_result=False)
     assert num_cpus, 'Unable to find /sys/devices/system/cpu/online'
     self._num_cpus = int(num_cpus[0].split('-')[-1])
     self._original_scaling_governor = None
 
   def DropRamCaches(self):
     """Drops the filesystem ram caches for performance testing."""
+    if not self._adb.IsRootEnabled():
+      self._adb.EnableAdbRoot()
+    self._adb.RunShellCommand('sync')
     self._adb.RunShellCommand('echo 3 > ' + PerfTestSetup._DROP_CACHES)
 
   def SetUp(self):
     """Sets up performance tests."""
     if not self._original_scaling_governor:
       self._original_scaling_governor = self._adb.GetFileContents(
           PerfTestSetup._SCALING_GOVERNOR % 0,
           log_result=False)[0]
       self._SetScalingGovernorInternal('performance')
     self.DropRamCaches()
 
   def TearDown(self):
     """Tears down performance tests."""
     if self._original_scaling_governor:
       self._SetScalingGovernorInternal(self._original_scaling_governor)
     self._original_scaling_governor = None
 
   def _SetScalingGovernorInternal(self, value):
     for cpu in range(self._num_cpus):
       self._adb.RunShellCommand(
           ('echo %s > ' + PerfTestSetup._SCALING_GOVERNOR) % (value, cpu))