Perform context disposal garbage collections only if contexts disposals happen at a high rate.

src/heap/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_HEAP_GC_TRACER_H_
 #define V8_HEAP_GC_TRACER_H_
 
 #include "src/base/platform/platform.h"
 
 namespace v8 {
@@ skipping 127 matching lines @@
 
     // Time spent in the mutator during the end of the last garbage collection
     // to the beginning of the next garbage collection.
     double duration_;
 
     // Memory allocated in the new space during the end of the last garbage
     // collection to the beginning of the next garbage collection.
     intptr_t allocation_in_bytes_;
   };
 
+
+  class ContextDisposalEvent {
+   public:
+    // Default constructor leaves the event uninitialized.
+    ContextDisposalEvent() {}
+
+    explicit ContextDisposalEvent(double time);
+
+    // Time when context disposal event happened.
+    double time_;
+  };
+
+
   class Event {
    public:
     enum Type { SCAVENGER = 0, MARK_COMPACTOR = 1, START = 2 };
 
     // Default constructor leaves the event uninitialized.
     Event() {}
 
     Event(Type type, const char* gc_reason, const char* collector_reason);
 
     // Returns a string describing the event type.
@@ skipping 76 matching lines @@
     // Amounts of time spent in different scopes during GC.
     double scopes[Scope::NUMBER_OF_SCOPES];
   };
 
   static const int kRingBufferMaxSize = 10;
 
   typedef RingBuffer<Event, kRingBufferMaxSize> EventBuffer;
 
   typedef RingBuffer<AllocationEvent, kRingBufferMaxSize> AllocationEventBuffer;
 
+  typedef RingBuffer<ContextDisposalEvent, kRingBufferMaxSize>
+      ContextDisposalEventBuffer;
+
   explicit GCTracer(Heap* heap);
 
   // 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 allocation throughput event.
   void AddNewSpaceAllocationTime(double duration, intptr_t allocation_in_bytes);
 
+  void AddContextDisposalTime(double time);
+
   // Log an incremental marking step.
   void AddIncrementalMarkingStep(double duration, intptr_t bytes);
 
   // Log time spent in marking.
   void AddMarkingTime(double duration) {
     cumulative_marking_duration_ += duration;
   }
 
   // Time spent in marking.
   double cumulative_marking_duration() const {
@@ skipping 49 matching lines @@
   intptr_t ScavengeSpeedInBytesPerMillisecond() const;
 
   // Compute the max mark-sweep speed in bytes/millisecond.
   // Returns 0 if no events have been recorded.
   intptr_t MarkCompactSpeedInBytesPerMillisecond() const;
 
   // Allocation throughput in the new space in bytes/millisecond.
   // Returns 0 if no events have been recorded.
   intptr_t NewSpaceAllocationThroughputInBytesPerMillisecond() const;
 
+  // Computes the context disposal rate in milliseconds. It takes the time
+  // frame of the first and last context disposal event and devides it by the
+  // number of recorded events.
+  // Returns 0 if no events have been recorded.
+  double ContextDisposalRateInMilliseconds() 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.
@@ skipping 17 matching lines @@
 
   // RingBuffers for SCAVENGER events.
   EventBuffer scavenger_events_;
 
   // RingBuffers for MARK_COMPACTOR events.
   EventBuffer mark_compactor_events_;
 
   // RingBuffer for allocation events.
   AllocationEventBuffer allocation_events_;
 
+  ContextDisposalEventBuffer context_disposal_events_;
+
   // Cumulative number of incremental marking steps since creation of tracer.
   int cumulative_incremental_marking_steps_;
 
   // Cumulative size of incremental marking steps (in bytes) since creation of
   // tracer.
   intptr_t cumulative_incremental_marking_bytes_;
 
   // Cumulative duration of incremental marking steps since creation of tracer.
   double cumulative_incremental_marking_duration_;
 
@@ skipping 20 matching lines @@
   // Holds the new space top pointer recorded at the end of the last garbage
   // collection.
   intptr_t new_space_top_after_gc_;
 
   DISALLOW_COPY_AND_ASSIGN(GCTracer);
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_GC_TRACER_H_