Add event statistics to GCTracer.

src/gc-tracer.h

 // 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.
 
 #ifndef V8_GC_TRACER_H_
 #define V8_GC_TRACER_H_
 
 namespace v8 {
 namespace internal {
 
@@ skipping 184 matching lines @@
   // Start collecting data.
   void Start(GarbageCollector collector, const char* gc_reason,
              const char* collector_reason);
 
   // Stop collecting data and print results.
   void Stop();
 
   // Log an incremental marking step.
   void AddIncrementalMarkingStep(double duration);
 
+  // Compute the mean duration of the last scavenger events. Returns 0 if no
+  // events have been recorded.
+  double MeanScavengerDuration() const {
+    return MeanDuration(scavenger_events_);
+  }
+
+  // Compute the max duration of the last scavenger events. Returns 0 if no
+  // events have been recorded.
+  double MaxScavengerDuration() const { return MaxDuration(scavenger_events_); }
+
+  // Compute the mean duration of the last mark compactor events. Returns 0 if
+  // no events have been recorded.
+  double MeanMarkCompactorDuration() const {
+    return MeanDuration(mark_compactor_events_);
+  }
+
+  // Compute the max duration of the last mark compactor events. Return 0 if no
+  // events have been recorded.
+  double MaxMarkCompactorDuration() const {
+    return MaxDuration(mark_compactor_events_);
+  }
+
+  // Compute the mean step duration of the last incremental marking round.
+  // Returns 0 if no incremental marking round has been completed.
+  double MeanIncrementalMarkingDuration() const;
+
+  // Compute the max step duration of the last incremental marking round.
+  // Returns 0 if no incremental marking round has been completed.
+  double MaxIncrementalMarkingDuration() const;
+
  private:
   // Print one detailed trace line in name=value format.
   // TODO(ernstm): Move to Heap.
   void PrintNVP() const;
 
   // Print one trace line.
   // TODO(ernstm): Move to Heap.
   void Print() const;
 
+  // Compute the mean duration of the events in the given ring buffer.
+  double MeanDuration(const EventBuffer& events) const;
+
+  // Compute the max duration of the events in the given ring buffer.
+  double MaxDuration(const EventBuffer& events) const;
+
   // Pointer to the heap that owns this tracer.
   Heap* heap_;
 
   // Current tracer event. Populated during Start/Stop cycle. Valid after Stop()
   // has returned.
   Event current_;
 
   // Previous tracer event.
   Event previous_;
 
@@ skipping 14 matching lines @@
 
   // Longest incremental marking step since start of marking.
   double longest_incremental_marking_step_;
 
   DISALLOW_COPY_AND_ASSIGN(GCTracer);
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_GC_TRACER_H_