1# Copyright 2013 The Chromium Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5import atexit
6import logging
7
8from pylib import android_commands
9from pylib.device import device_utils
10
11class PerfControl(object):
12  """Provides methods for setting the performance mode of a device."""
13  _SCALING_GOVERNOR_FMT = (
14      '/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor')
15  _CPU_ONLINE_FMT = '/sys/devices/system/cpu/cpu%d/online'
16  _KERNEL_MAX = '/sys/devices/system/cpu/kernel_max'
17
18  def __init__(self, device):
19    # TODO(jbudorick) Remove once telemetry gets switched over.
20    if isinstance(device, android_commands.AndroidCommands):
21      device = device_utils.DeviceUtils(device)
22    self._device = device
23    cpu_files = self._device.RunShellCommand(
24      'ls -d /sys/devices/system/cpu/cpu[0-9]*')
25    self._num_cpu_cores = len(cpu_files)
26    assert self._num_cpu_cores > 0, 'Failed to detect CPUs.'
27    logging.info('Number of CPUs: %d', self._num_cpu_cores)
28    self._have_mpdecision = self._device.FileExists('/system/bin/mpdecision')
29
30  def SetHighPerfMode(self):
31    """Sets the highest possible performance mode for the device."""
32    if not self._device.old_interface.IsRootEnabled():
33      message = 'Need root for performance mode. Results may be NOISY!!'
34      logging.warning(message)
35      # Add an additional warning at exit, such that it's clear that any results
36      # may be different/noisy (due to the lack of intended performance mode).
37      atexit.register(logging.warning, message)
38      return
39    # TODO(epenner): Enable on all devices (http://crbug.com/383566)
40    if 'Nexus 4' == self._device.old_interface.GetProductModel():
41      self._ForceAllCpusOnline(True)
42      if not self._AllCpusAreOnline():
43        logging.warning('Failed to force CPUs online. Results may be NOISY!')
44    self._SetScalingGovernorInternal('performance')
45
46  def SetPerfProfilingMode(self):
47    """Enables all cores for reliable perf profiling."""
48    self._ForceAllCpusOnline(True)
49    self._SetScalingGovernorInternal('performance')
50    if not self._AllCpusAreOnline():
51      if not self._device.old_interface.IsRootEnabled():
52        raise RuntimeError('Need root to force CPUs online.')
53      raise RuntimeError('Failed to force CPUs online.')
54
55  def SetDefaultPerfMode(self):
56    """Sets the performance mode for the device to its default mode."""
57    if not self._device.old_interface.IsRootEnabled():
58      return
59    product_model = self._device.GetProp('ro.product.model')
60    governor_mode = {
61        'GT-I9300': 'pegasusq',
62        'Galaxy Nexus': 'interactive',
63        'Nexus 4': 'ondemand',
64        'Nexus 7': 'interactive',
65        'Nexus 10': 'interactive'
66    }.get(product_model, 'ondemand')
67    self._SetScalingGovernorInternal(governor_mode)
68    self._ForceAllCpusOnline(False)
69
70  def _SetScalingGovernorInternal(self, value):
71    cpu_cores = ' '.join([str(x) for x in range(self._num_cpu_cores)])
72    script = ('for CPU in %s; do\n'
73        '  FILE="/sys/devices/system/cpu/cpu$CPU/cpufreq/scaling_governor"\n'
74        '  test -e $FILE && echo %s > $FILE\n'
75        'done\n') % (cpu_cores, value)
76    logging.info('Setting scaling governor mode: %s', value)
77    self._device.RunShellCommand(script, as_root=True)
78
79  def _AllCpusAreOnline(self):
80    for cpu in range(1, self._num_cpu_cores):
81      online_path = PerfControl._CPU_ONLINE_FMT % cpu
82      # TODO(epenner): Investigate why file may be missing
83      # (http://crbug.com/397118)
84      if not self._device.FileExists(online_path) or \
85            self._device.ReadFile(online_path)[0] == '0':
86        return False
87    return True
88
89  def _ForceAllCpusOnline(self, force_online):
90    """Enable all CPUs on a device.
91
92    Some vendors (or only Qualcomm?) hot-plug their CPUs, which can add noise
93    to measurements:
94    - In perf, samples are only taken for the CPUs that are online when the
95      measurement is started.
96    - The scaling governor can't be set for an offline CPU and frequency scaling
97      on newly enabled CPUs adds noise to both perf and tracing measurements.
98
99    It appears Qualcomm is the only vendor that hot-plugs CPUs, and on Qualcomm
100    this is done by "mpdecision".
101
102    """
103    if self._have_mpdecision:
104      script = 'stop mpdecision' if force_online else 'start mpdecision'
105      self._device.RunShellCommand(script, as_root=True)
106
107    if not self._have_mpdecision and not self._AllCpusAreOnline():
108      logging.warning('Unexpected cpu hot plugging detected.')
109
110    if not force_online:
111      return
112
113    for cpu in range(self._num_cpu_cores):
114      online_path = PerfControl._CPU_ONLINE_FMT % cpu
115      self._device.WriteFile(online_path, '1', as_root=True)
116