Make new space allocation throughput estimation more accurate.

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 123 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(Scope);
   };
 
 
   class AllocationEvent {
    public:
     // Default constructor leaves the event uninitialized.
     AllocationEvent() {}
 
-    AllocationEvent(double duration, intptr_t allocation_in_bytes);
+    AllocationEvent(double duration, size_t allocation_in_bytes);
 
-    // Time spent in the mutator during the end of the last garbage collection
-    // to the beginning of the next garbage collection.
+    // Time spent in the mutator during the end of the last sample to the
+    // beginning of the next sample.
     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_;
+    // Memory allocated in the new space during the end of the last sample
+    // to the beginning of the next sample
+    size_t allocation_in_bytes_;
   };
 
 
   class ContextDisposalEvent {
    public:
     // Default constructor leaves the event uninitialized.
     ContextDisposalEvent() {}
 
     explicit ContextDisposalEvent(double time);
 
@@ skipping 109 matching lines @@
     double longest_incremental_marking_step;
 
     // Amounts of time spent in different scopes during GC.
     double scopes[Scope::NUMBER_OF_SCOPES];
   };
 
   static const size_t kRingBufferMaxSize = 10;
 
   typedef RingBuffer<Event, kRingBufferMaxSize> EventBuffer;
 
   typedef RingBuffer<AllocationEvent, kRingBufferMaxSize> AllocationEventBuffer;

[Hannes Payer (out of office), 2015/05/12 17:04:17]

I am wondering about the size of the ring buffer. You get now finer grained
samples. I think the buffer should be bigger for that to average out spikes. 

[ulan, 2015/05/18 12:45:51]

Adding a new allocation event for each idle notification made the result more
noisy. I reworked this part:
- Add allocation events to the buffer only after GC (as before).
- Separately accumulate (duration_ms, allocated_bytes) since the last GC (see
new_space_allocation_duration_since_gc_, new_space_allocation_in_bytes_since_gc_
in gc-tracer.h)

 
   typedef RingBuffer<ContextDisposalEvent, kRingBufferMaxSize>
       ContextDisposalEventBuffer;
 
   typedef RingBuffer<SurvivalEvent, kRingBufferMaxSize> SurvivalEventBuffer;
 
   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(GarbageCollector collector);
 
   // Log an allocation throughput event.
-  void AddNewSpaceAllocationTime(double duration, intptr_t allocation_in_bytes);
+  void SampleNewSpaceAllocation(double current_ms, size_t counter_bytes);
 
   void AddContextDisposalTime(double time);
 
   void AddSurvivalRatio(double survival_ratio);
 
   // Log an incremental marking step.
   void AddIncrementalMarkingStep(double duration, intptr_t bytes);
 
   // Log time spent in marking.
   void AddMarkingTime(double duration) {
@@ skipping 63 matching lines @@
   // Returns 0 if no events have been recorded.
   intptr_t MarkCompactSpeedInBytesPerMillisecond() const;
 
   // Compute the average incremental mark-sweep finalize speed in
   // bytes/millisecond.
   // Returns 0 if no events have been recorded.
   intptr_t FinalIncrementalMarkCompactSpeedInBytesPerMillisecond() const;
 
   // Allocation throughput in the new space in bytes/millisecond.
   // Returns 0 if no events have been recorded.
-  intptr_t NewSpaceAllocationThroughputInBytesPerMillisecond() const;
+  size_t NewSpaceAllocationThroughputInBytesPerMillisecond() const;
 
   // Computes the context disposal rate in milliseconds. It takes the time
   // frame of the first recorded context disposal to the current time and
   // divides it by the number of recorded events.
   // Returns 0 if no events have been recorded.
   double ContextDisposalRateInMilliseconds() const;
 
   // Computes the average survival ratio based on the last recorded survival
   // events.
   // Returns 0 if no events have been recorded.
@@ skipping 84 matching lines @@
 
   // Total sweeping time on the main thread.
   // This timer is precise when run with --print-cumulative-gc-stat
   // TODO(hpayer): Account for sweeping time on sweeper threads. Add a
   // different field for that.
   // TODO(hpayer): This timer right now just holds the sweeping time
   // of the initial atomic sweeping pause. Make sure that it accumulates
   // all sweeping operations performed on the main thread.
   double cumulative_sweeping_duration_;
 
-  // Holds the new space top pointer recorded at the end of the last garbage
-  // collection.
-  intptr_t new_space_top_after_gc_;
+  double new_space_allocation_time_ms_;

[Hannes Payer (out of office), 2015/05/12 17:04:17]

Please describe the added fields.

[ulan, 2015/05/18 12:45:51]

Done.

+  size_t new_space_allocation_counter_bytes_;
 
   // Counts how many tracers were started without stopping.
   int start_counter_;
 
   DISALLOW_COPY_AND_ASSIGN(GCTracer);
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_GC_TRACER_H_