Add event statistics to GCTracer.

src/gc-tracer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/gc-tracer.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 250 matching lines @@
            current_.incremental_marking_steps -
                previous_mark_compactor_event_.incremental_marking_steps);
     PrintF("stepstook=%.1f ",
            current_.incremental_marking_duration -
                previous_mark_compactor_event_.incremental_marking_duration);
     PrintF("longeststep=%.1f ", current_.longest_incremental_marking_step);
   }
 
   PrintF("\n");
 }
+
+
+double GCTracer::MeanDuration(const EventBuffer& events) const {
+  if (events.empty()) return 0.0;
+
+  double mean = 0.0;
+  EventBuffer::const_iterator iter = events.begin();
+  while (iter != events.end()) {
+    mean += iter->end_time - iter->start_time;
+    ++iter;
+  }
+
+  return mean / events.size();
+}
+
+
+double GCTracer::MaxDuration(const EventBuffer& events) const {
+  if (events.empty()) return 0.0;
+
+  double maximum = 0.0f;
+  EventBuffer::const_iterator iter = events.begin();
+  while (iter != events.end()) {
+    maximum = Max(iter->end_time - iter->start_time, maximum);
+    ++iter;
+  }
+
+  return maximum;
+}
+
+
+double GCTracer::MeanIncrementalMarkingDuration() const {
+  if (mark_compactor_events_.empty()) return 0.0;
+
+  EventBuffer::const_iterator last_mc = mark_compactor_events_.begin();
+  return last_mc->incremental_marking_duration /
+         last_mc->incremental_marking_steps;
+}
+
+
+double GCTracer::MaxIncrementalMarkingDuration() const {
+  if (mark_compactor_events_.empty()) return 0.0;
+
+  EventBuffer::const_iterator last_mc = mark_compactor_events_.begin();
+  return last_mc->longest_incremental_marking_step;
+}
 }
 }  // namespace v8::internal