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

tools/perf/metrics/memory.py

Index: tools/perf/metrics/memory.py
diff --git a/tools/perf/metrics/memory.py b/tools/perf/metrics/memory.py
index 74fe26efe0bf60da53e3cceecc93f05ecb6e1848..fc9159311cd473d683153885e40824328b752041 100644
--- a/tools/perf/metrics/memory.py
+++ b/tools/perf/metrics/memory.py
@@ -41,6 +41,7 @@ class MemoryMetric(Metric):
     """
     for h in _HISTOGRAMS:
       histogram_data = histogram.GetHistogramData(h['type'], h['name'], tab)
+      # Histogram data may not be available

[qyearsley, 2013/08/12 20:57:48]

Not sure if it's best not to repeat this comment below, but it seems that
there's no harm in it.

       if not histogram_data:
         continue
       self._histogram_start_values[h['name']] = histogram_data
@@ -53,14 +54,20 @@ class MemoryMetric(Metric):
     """
     assert self._histogram_start_values, 'Must call Start() first'
     for h in _HISTOGRAMS:
+      # Histogram data may not be available
+      if h['name'] not in self._histogram_start_values:
+        continue
       histogram_data = histogram.GetHistogramData(h['type'], h['name'], tab)
-      self._histogram_delta_values = histogram.SubtractHistogram(
+      self._histogram_delta_values[h['name']] = histogram.SubtractHistogram(

[qyearsley, 2013/08/12 20:57:48]

I forgot to use self._histogram_delta_values as a dictionary here before.

           histogram_data, self._histogram_start_values[h['name']])

[qyearsley, 2013/08/12 20:57:48]

Here (and in AddResults) I'm assuming that if histogram data was set before for
a particular histogram name, then histogram.GetHistogramData will return new
histogram data; I think this is a reasonable assumption.

 
   def AddResults(self, tab, results):
     """Add results for this page to the results object."""
     assert self._histogram_delta_values, 'Must call Stop() first'
     for h in _HISTOGRAMS:
+      # Histogram data may not be available
+      if h['name'] not in self._histogram_delta_values:
+        continue
       histogram_data = self._histogram_delta_values[h['name']]
       results.Add(h['name'], h['units'], histogram_data,
                   data_type='unimportant-histogram')