tools/perf/metrics/cpu.py

   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
   5 from metrics import Metric
   6
   7 class CpuMetric(Metric):
   8   """Calulates CPU load over a span of time."""
   9
  10   def __init__(self, browser):
  11     super(CpuMetric, self).__init__()
  12     self._results = None
  13     self._browser = browser
  14     self._start_cpu = None
  15
  16   def DidStartBrowser(self, browser):
  17     # Save the browser object so that cpu_stats can be accessed later.
  18     self._browser = browser
  19
  20   def Start(self, page, tab):
  21     self._start_cpu = self._browser.cpu_stats
  22
  23   def Stop(self, page, tab):
  24     assert self._start_cpu, 'Must call Start() first'
  25     self._results = _SubtractCpuStats(self._browser.cpu_stats, self._start_cpu)
  26
  27   # Optional argument trace_name is not in base class Metric.
  28   # pylint: disable=W0221
  29   def AddResults(self, tab, results, trace_name='cpu_utilization'):
  30     assert self._results, 'Must call Stop() first'
  31     # Add a result for each process type.
  32     for process_type in self._results:
  33       trace_name = '%s_%s' % (trace_name, process_type.lower())
  34       cpu_percent = 100 * self._results[process_type]
  35       results.Add(trace_name, '%', cpu_percent, chart_name='cpu_utilization',
  36                   data_type='unimportant')
  37
  38
  39 def _SubtractCpuStats(cpu_stats, start_cpu_stats):
  40   """Computes average cpu usage over a time period for different process types.
  41
  42   Each of the two cpu_stats arguments is a dict with the following format:
  43       {'Browser': {'CpuProcessTime': ..., 'TotalTime': ...},
  44        'Renderer': {'CpuProcessTime': ..., 'TotalTime': ...}
  45        'Gpu': {'CpuProcessTime': ..., 'TotalTime': ...}}
  46
  47   The 'CpuProcessTime' fields represent the number of seconds of CPU time
  48   spent in each process, and total time is the number of real seconds
  49   that have passed (this may be a Unix timestamp).
  50
  51   Returns:
  52     A dict of process type names (Browser, Renderer, etc.) to ratios of cpu
  53     time used to total time elapsed.
  54   """
  55   cpu_usage = {}
  56   for process_type in cpu_stats:
  57     assert process_type in start_cpu_stats, 'Mismatching process types'
  58     # Skip any process_types that are empty.
  59     if (not cpu_stats[process_type]) or (not start_cpu_stats[process_type]):
  60       continue
  61     cpu_process_time = (cpu_stats[process_type]['CpuProcessTime'] -
  62                         start_cpu_stats[process_type]['CpuProcessTime'])
  63     total_time = (cpu_stats[process_type]['TotalTime'] -
  64                   start_cpu_stats[process_type]['TotalTime'])
  65     assert total_time > 0, 'Expected total_time > 0, was: %d' % total_time
  66     cpu_usage[process_type] = float(cpu_process_time) / total_time
  67   return cpu_usage
  68