Move memory-related histogram data collection to metrics/memory.py

tools/perf/metrics/histogram.py

 # Copyright 2013 The Chromium Authors. All rights reserved.

[qyearsley, 2013/08/08 17:35:52]

This module contains basically what was just in 'histogram_util.py'. It could
also be changed to histogram_util, since it's possible that calling it just
'histogram' and putting it in this metrics/ directory might suggest that it
contains a subclass of Metric.

 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
-from metrics import histogram_util
+
+"""This is a helper module to get and manipulate histogram data.
+
+The histogram data is the same data as is visible from "chrome://histograms".
+More information can be found at: chromium/src/base/metrics/histogram.h
+
+Histogram data is collected with either the window.statsCollectionController
+object or the window.domAutomationController object.
+"""
+
+import json
+import logging
 
 BROWSER_HISTOGRAM = 'browser_histogram'
 RENDERER_HISTOGRAM = 'renderer_histogram'
 
-class HistogramMetric(object):
-  def __init__(self, histogram, histogram_type):
-    self.name = histogram['name']
-    self.units = histogram['units']
-    self.histogram_type = histogram_type
-    self._start_values = dict()
+def GetHistogramData(histogram_type, histogram_name, tab):

[qyearsley, 2013/08/08 17:35:52]

I renamed GetHistogramFromDomAutomation to GetHistogramData because the means by
which the histogram data is obtained is probably not important to other classes
and doesn't need to be put in the function name. But if you think
GetHistogramFromDomAutomation is more descriptive, this name could be used
instead.

+  """Get a json serialization of a histogram."""
+  assert histogram_type in [BROWSER_HISTOGRAM, RENDERER_HISTOGRAM]
+  function = 'getHistogram'
+  if histogram_type == BROWSER_HISTOGRAM:
+    function = 'getBrowserHistogram'
+  # TODO(jeremy): Remove references to
+  # domAutomationController when we update the reference builds.
+  return tab.EvaluateJavaScript(
+      '(window.statsCollectionController ? '
+      'statsCollectionController : '
+      'domAutomationController).%s("%s")' %
+      (function, histogram_name))
 
-  def Start(self, page, tab):
-    """Get the starting value for the histogram. This value will then be
-    subtracted from the actual measurement."""
-    data = self._GetHistogramFromDomAutomation(tab)
-    if data:
-      self._start_values[page.url + self.name] = data
 
-  def GetValue(self, page, tab, results):
-    data = self._GetHistogramFromDomAutomation(tab)
-    if not data:
-      return
-    new_histogram = histogram_util.SubtractHistogram(
-        data, self._start_values[page.url + self.name])
-    results.Add(self.name, self.units, new_histogram,
-                data_type='unimportant-histogram')
+def SubtractHistogram(histogram_json, start_histogram_json):
+  """Subtracts a previous histogram from a histogram.
 
-  @property
-  def histogram_function(self):
-    if self.histogram_type == BROWSER_HISTOGRAM:
-      return 'getBrowserHistogram'
-    return 'getHistogram'
+  Both parameters and the returned result are json serializations.
+  """
+  start_histogram = json.loads(start_histogram_json)
+  # It's ok if the start histogram is empty (we had no data, maybe even no
+  # histogram at all, at the start of the test).
+  if 'buckets' not in start_histogram:
+    return histogram_json
 
-  def _GetHistogramFromDomAutomation(self, tab):
-    return histogram_util.GetHistogramFromDomAutomation(
-        self.histogram_function, self.name, tab)
+  histogram = json.loads(histogram_json)
+  if ('pid' in start_histogram and 'pid' in histogram
+      and start_histogram['pid'] != histogram['pid']):
+    raise Exception(
+        'Trying to compare histograms from different processes (%d and %d)'
+        % (start_histogram['pid'], histogram['pid']))
+
+  start_histogram_buckets = dict()
+  for b in start_histogram['buckets']:
+    start_histogram_buckets[b['low']] = b['count']
+
+  new_buckets = []
+  for b in histogram['buckets']:
+    new_bucket = b
+    low = b['low']
+    if low in start_histogram_buckets:
+      new_bucket['count'] = b['count'] - start_histogram_buckets[low]
+      if new_bucket['count'] < 0:
+        logging.error('Histogram subtraction error, starting histogram most '
+                      'probably invalid.')
+    if new_bucket['count']:
+      new_buckets.append(new_bucket)
+  histogram['buckets'] = new_buckets
+  histogram['count'] -= start_histogram['count']
+
+  return json.dumps(histogram)
+