Android: upstream latest changes for build/android.

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
 
 # 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 45 matching lines @@
     # 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 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."""
+    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))