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 69
