Telemetry: adds CPU frequency stats.

tools/perf/metrics/cpu.py

Index: tools/perf/metrics/cpu.py
diff --git a/tools/perf/metrics/cpu.py b/tools/perf/metrics/cpu.py
index aa57b073078a791ea945e954f030c1c3cf9b3d9a..c813f86819302af8605bace1a76ec782ed1248b6 100644
--- a/tools/perf/metrics/cpu.py
+++ b/tools/perf/metrics/cpu.py
@@ -30,10 +30,26 @@ class CpuMetric(Metric):
     assert self._results, 'Must call Stop() first'
     # Add a result for each process type.
     for process_type in self._results:
+      if process_type == 'Global':
+        continue
       trace_name_for_process = '%s_%s' % (trace_name, process_type.lower())
       cpu_percent = 100 * self._results[process_type]
       results.Add(trace_name_for_process, '%', cpu_percent,
                   chart_name='cpu_utilization', data_type='unimportant')
+    # Add a result for Global CPU stats: these are system-wide metrics,
+    # not per process as the ones above.
+    if 'Global' in self._results:
+      total_time = 0.0
+      frequency_sum = 0.0
+      for frequency, time_in_state in \
+          self._results['Global']['GlobalCpuFrequencyStats'].iteritems():
+        frequency_sum += (frequency * time_in_state)
+        total_time += time_in_state
+      if total_time:
+        results.Add('average_frequency_mhz', 'MHz',
+                    round((frequency_sum / total_time) / 1000000.0, 2),
+                    chart_name='cpu_frequency',
+                    data_type='unimportant')
 
 
 def _SubtractCpuStats(cpu_stats, start_cpu_stats):
@@ -55,8 +71,10 @@ def _SubtractCpuStats(cpu_stats, start_cpu_stats):
   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]):
+    # Skip any process_types that are empty or Global.
+    if ((not cpu_stats[process_type]) or
+        (not start_cpu_stats[process_type]) or
+        process_type == 'Global'):
       continue
     cpu_process_time = (cpu_stats[process_type]['CpuProcessTime'] -
                         start_cpu_stats[process_type]['CpuProcessTime'])
@@ -64,5 +82,16 @@ def _SubtractCpuStats(cpu_stats, start_cpu_stats):
                   start_cpu_stats[process_type]['TotalTime'])
     assert total_time > 0, 'Expected total_time > 0, was: %d' % total_time
     cpu_usage[process_type] = float(cpu_process_time) / total_time
-  return cpu_usage
 
+  if 'Global' not in cpu_stats:
+    return cpu_usage
+
+  frequency_stats = cpu_stats['Global']['GlobalCpuFrequencyStats']
+  start_frequency_stats = start_cpu_stats['Global']['GlobalCpuFrequencyStats']
+  total_frequency_stats = {}
+  for k in frequency_stats.iterkeys():
+    total_frequency_stats[k] = frequency_stats[k] - start_frequency_stats[k]
+
+  cpu_usage['Global'] = {}
+  cpu_usage['Global']['GlobalCpuFrequencyStats'] = total_frequency_stats
+  return cpu_usage