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# 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.
from metrics import Metric
from telemetry.value import scalar
class CpuMetric(Metric):
"""Calulates CPU load over a span of time."""
def __init__(self, browser):
super(CpuMetric, self).__init__()
self._browser = browser
self._start_cpu = None
self._stop_cpu = None
def DidStartBrowser(self, browser):
# Save the browser object so that cpu_stats can be accessed later.
self._browser = browser
def Start(self, page, tab):
self._start_cpu = self._browser.cpu_stats
def Stop(self, page, tab):
assert self._start_cpu, 'Must call Start() first'
self._stop_cpu = self._browser.cpu_stats
# Optional argument trace_name is not in base class Metric.
# pylint: disable=W0221
def AddResults(self, tab, results, trace_name='cpu_utilization'):
assert self._stop_cpu, 'Must call Stop() first'
cpu_stats = _SubtractCpuStats(self._stop_cpu, self._start_cpu)
# Add a result for each process type.
for process_type in cpu_stats:
trace_name_for_process = '%s_%s' % (trace_name, process_type.lower())
cpu_percent = 100 * cpu_stats[process_type]
results.AddValue(scalar.ScalarValue(
results.current_page, 'cpu_utilization.%s' % trace_name_for_process,
'%', cpu_percent, important=False))
def _SubtractCpuStats(cpu_stats, start_cpu_stats):
"""Computes average cpu usage over a time period for different process types.
Each of the two cpu_stats arguments is a dict with the following format:
{'Browser': {'CpuProcessTime': ..., 'TotalTime': ...},
'Renderer': {'CpuProcessTime': ..., 'TotalTime': ...}
'Gpu': {'CpuProcessTime': ..., 'TotalTime': ...}}
The 'CpuProcessTime' fields represent the number of seconds of CPU time
spent in each process, and total time is the number of real seconds
that have passed (this may be a Unix timestamp).
Returns:
A dict of process type names (Browser, Renderer, etc.) to ratios of cpu
time used to total time elapsed.
"""
cpu_usage = {}
for process_type in cpu_stats:
assert process_type in start_cpu_stats, 'Mismatching process types'
# Skip any process_types that are empty.
if (not cpu_stats[process_type]) or (not start_cpu_stats[process_type]):
continue
cpu_process_time = (cpu_stats[process_type]['CpuProcessTime'] -
start_cpu_stats[process_type]['CpuProcessTime'])
total_time = (cpu_stats[process_type]['TotalTime'] -
start_cpu_stats[process_type]['TotalTime'])
# Fix overflow for 32-bit jiffie counter, 64-bit counter will not overflow.
# Linux kernel starts with a value close to an overflow, so correction is
# necessary.
if total_time < 0:
total_time += 2**32
# Assert that the arguments were given in the correct order.
assert total_time > 0 and total_time < 2**31, (
'Expected total_time > 0, was: %d' % total_time)
cpu_usage[process_type] = float(cpu_process_time) / total_time
return cpu_usage
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