Make single shell call in _SetScalingGovernorInternal

build/android/pylib/perf/perf_control.py

 # Copyright 2013 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 atexit
 import logging
 
 from pylib import android_commands
 from pylib.device import device_utils
 
@@ skipping 50 matching lines @@
         'GT-I9300': 'pegasusq',
         'Galaxy Nexus': 'interactive',
         'Nexus 4': 'ondemand',
         'Nexus 7': 'interactive',
         'Nexus 10': 'interactive'
     }.get(product_model, 'ondemand')
     self._SetScalingGovernorInternal(governor_mode)
     self._ForceAllCpusOnline(False)
 
   def _SetScalingGovernorInternal(self, value):
-    for cpu in range(self._num_cpu_cores):
-      scaling_governor_file = PerfControl._SCALING_GOVERNOR_FMT % cpu
-      if self._device.FileExists(scaling_governor_file):
-        logging.info('Writing scaling governor mode \'%s\' -> %s',
-                     value, scaling_governor_file)
-        self._device.WriteFile(scaling_governor_file, value, as_root=True)
+    cpu_cores = ' '.join([str(x) for x in range(self._num_cpu_cores)])
+    script = ('for CPU in %s; do\n'
+        '  FILE="/sys/devices/system/cpu/cpu$CPU/cpufreq/scaling_governor"\n'
+        '  test -e $FILE && echo %s > $FILE\n'
+        'done\n') % (cpu_cores, value)
+    logging.info('Setting scaling governor mode: %s', value)
+    self._device.RunShellCommand(script, as_root=True)
 
   def _AllCpusAreOnline(self):
     for cpu in range(self._num_cpu_cores):
       online_path = PerfControl._CPU_ONLINE_FMT % cpu
       # TODO(epenner): Investigate why file may be missing
       # (http://crbug.com/397118)
       if not self._device.FileExists(online_path) or \
             self._device.ReadFile(online_path)[0] == '0':
         return False
     return True
@@ skipping 18 matching lines @@
 
     if not self._have_mpdecision and not self._AllCpusAreOnline():
       logging.warning('Unexpected cpu hot plugging detected.')
 
     if not force_online:
       return
 
     for cpu in range(self._num_cpu_cores):
       online_path = PerfControl._CPU_ONLINE_FMT % cpu
       self._device.WriteFile(online_path, '1', as_root=True)