src/heap/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/heap/gc-tracer.h"

#include "src/counters.h"
#include "src/heap/heap-inl.h"
#include "src/isolate.h"

namespace v8 {
namespace internal {

static intptr_t CountTotalHolesSize(Heap* heap) {
  intptr_t holes_size = 0;
  OldSpaces spaces(heap);
  for (OldSpace* space = spaces.next(); space != NULL; space = spaces.next()) {
    holes_size += space->Waste() + space->Available();
  }
  return holes_size;
}


GCTracer::Scope::Scope(GCTracer* tracer, ScopeId scope)
    : tracer_(tracer), scope_(scope) {
  start_time_ = tracer_->heap_->MonotonicallyIncreasingTimeInMs();
}


GCTracer::Scope::~Scope() {
  DCHECK(scope_ < NUMBER_OF_SCOPES);  // scope_ is unsigned.
  tracer_->current_.scopes[scope_] +=
      tracer_->heap_->MonotonicallyIncreasingTimeInMs() - start_time_;
}


GCTracer::AllocationEvent::AllocationEvent(double duration,
                                           size_t allocation_in_bytes) {
  duration_ = duration;
  allocation_in_bytes_ = allocation_in_bytes;
}


GCTracer::ContextDisposalEvent::ContextDisposalEvent(double time) {
  time_ = time;
}


GCTracer::SurvivalEvent::SurvivalEvent(double promotion_ratio) {
  promotion_ratio_ = promotion_ratio;
}


GCTracer::Event::Event(Type type, const char* gc_reason,
                       const char* collector_reason)
    : type(type),
      gc_reason(gc_reason),
      collector_reason(collector_reason),
      start_time(0.0),
      end_time(0.0),
      reduce_memory(false),
      start_object_size(0),
      end_object_size(0),
      start_memory_size(0),
      end_memory_size(0),
      start_holes_size(0),
      end_holes_size(0),
      cumulative_incremental_marking_steps(0),
      incremental_marking_steps(0),
      cumulative_incremental_marking_bytes(0),
      incremental_marking_bytes(0),
      cumulative_incremental_marking_duration(0.0),
      incremental_marking_duration(0.0),
      cumulative_pure_incremental_marking_duration(0.0),
      pure_incremental_marking_duration(0.0),
      longest_incremental_marking_step(0.0) {
  for (int i = 0; i < Scope::NUMBER_OF_SCOPES; i++) {
    scopes[i] = 0;
  }
}


const char* GCTracer::Event::TypeName(bool short_name) const {
  switch (type) {
    case SCAVENGER:
      if (short_name) {
        return "s";
      } else {
        return "Scavenge";
      }
    case MARK_COMPACTOR:
    case INCREMENTAL_MARK_COMPACTOR:
      if (short_name) {
        return "ms";
      } else {
        return "Mark-sweep";
      }
    case START:
      if (short_name) {
        return "st";
      } else {
        return "Start";
      }
  }
  return "Unknown Event Type";
}


GCTracer::GCTracer(Heap* heap)
    : heap_(heap),
      cumulative_incremental_marking_steps_(0),
      cumulative_incremental_marking_bytes_(0),
      cumulative_incremental_marking_duration_(0.0),
      cumulative_pure_incremental_marking_duration_(0.0),
      longest_incremental_marking_step_(0.0),
      cumulative_incremental_marking_finalization_steps_(0),
      cumulative_incremental_marking_finalization_duration_(0.0),
      longest_incremental_marking_finalization_step_(0.0),
      cumulative_marking_duration_(0.0),
      cumulative_sweeping_duration_(0.0),
      allocation_time_ms_(0.0),
      new_space_allocation_counter_bytes_(0),
      old_generation_allocation_counter_bytes_(0),
      allocation_duration_since_gc_(0.0),
      new_space_allocation_in_bytes_since_gc_(0),
      old_generation_allocation_in_bytes_since_gc_(0),
      combined_mark_compact_speed_cache_(0.0),
      start_counter_(0) {
  current_ = Event(Event::START, NULL, NULL);
  current_.end_time = heap_->MonotonicallyIncreasingTimeInMs();
  previous_ = previous_incremental_mark_compactor_event_ = current_;
}


void GCTracer::Start(GarbageCollector collector, const char* gc_reason,
                     const char* collector_reason) {
  start_counter_++;
  if (start_counter_ != 1) return;

  previous_ = current_;
  double start_time = heap_->MonotonicallyIncreasingTimeInMs();
  SampleAllocation(start_time, heap_->NewSpaceAllocationCounter(),
                   heap_->OldGenerationAllocationCounter());
  if (current_.type == Event::INCREMENTAL_MARK_COMPACTOR)
    previous_incremental_mark_compactor_event_ = current_;

  if (collector == SCAVENGER) {
    current_ = Event(Event::SCAVENGER, gc_reason, collector_reason);
  } else if (collector == MARK_COMPACTOR) {
    if (heap_->incremental_marking()->WasActivated()) {
      current_ =
          Event(Event::INCREMENTAL_MARK_COMPACTOR, gc_reason, collector_reason);
    } else {
      current_ = Event(Event::MARK_COMPACTOR, gc_reason, collector_reason);
    }
  }

  current_.reduce_memory = heap_->ShouldReduceMemory();
  current_.start_time = start_time;
  current_.start_object_size = heap_->SizeOfObjects();
  current_.start_memory_size = heap_->isolate()->memory_allocator()->Size();
  current_.start_holes_size = CountTotalHolesSize(heap_);
  current_.new_space_object_size =
      heap_->new_space()->top() - heap_->new_space()->bottom();

  current_.cumulative_incremental_marking_steps =
      cumulative_incremental_marking_steps_;
  current_.cumulative_incremental_marking_bytes =
      cumulative_incremental_marking_bytes_;
  current_.cumulative_incremental_marking_duration =
      cumulative_incremental_marking_duration_;
  current_.cumulative_pure_incremental_marking_duration =
      cumulative_pure_incremental_marking_duration_;
  current_.longest_incremental_marking_step = longest_incremental_marking_step_;

  for (int i = 0; i < Scope::NUMBER_OF_SCOPES; i++) {
    current_.scopes[i] = 0;
  }
  int committed_memory = static_cast<int>(heap_->CommittedMemory() / KB);
  int used_memory = static_cast<int>(current_.start_object_size / KB);
  heap_->isolate()->counters()->aggregated_memory_heap_committed()->AddSample(
      start_time, committed_memory);
  heap_->isolate()->counters()->aggregated_memory_heap_used()->AddSample(
      start_time, used_memory);
}


void GCTracer::Stop(GarbageCollector collector) {
  start_counter_--;
  if (start_counter_ != 0) {
    Output("[Finished reentrant %s during %s.]\n",
           collector == SCAVENGER ? "Scavenge" : "Mark-sweep",
           current_.TypeName(false));
    return;
  }

  DCHECK(start_counter_ >= 0);
  DCHECK((collector == SCAVENGER && current_.type == Event::SCAVENGER) ||
         (collector == MARK_COMPACTOR &&
          (current_.type == Event::MARK_COMPACTOR ||
           current_.type == Event::INCREMENTAL_MARK_COMPACTOR)));

  current_.end_time = heap_->MonotonicallyIncreasingTimeInMs();
  current_.end_object_size = heap_->SizeOfObjects();
  current_.end_memory_size = heap_->isolate()->memory_allocator()->Size();
  current_.end_holes_size = CountTotalHolesSize(heap_);
  current_.survived_new_space_object_size = heap_->SurvivedNewSpaceObjectSize();

  AddAllocation(current_.end_time);

  int committed_memory = static_cast<int>(heap_->CommittedMemory() / KB);
  int used_memory = static_cast<int>(current_.end_object_size / KB);
  heap_->isolate()->counters()->aggregated_memory_heap_committed()->AddSample(
      current_.end_time, committed_memory);
  heap_->isolate()->counters()->aggregated_memory_heap_used()->AddSample(
      current_.end_time, used_memory);

  if (current_.type == Event::SCAVENGER) {
    current_.incremental_marking_steps =
        current_.cumulative_incremental_marking_steps -
        previous_.cumulative_incremental_marking_steps;
    current_.incremental_marking_bytes =
        current_.cumulative_incremental_marking_bytes -
        previous_.cumulative_incremental_marking_bytes;
    current_.incremental_marking_duration =
        current_.cumulative_incremental_marking_duration -
        previous_.cumulative_incremental_marking_duration;
    current_.pure_incremental_marking_duration =
        current_.cumulative_pure_incremental_marking_duration -
        previous_.cumulative_pure_incremental_marking_duration;
    scavenger_events_.push_front(current_);
  } else if (current_.type == Event::INCREMENTAL_MARK_COMPACTOR) {
    current_.incremental_marking_steps =
        current_.cumulative_incremental_marking_steps -
        previous_incremental_mark_compactor_event_
            .cumulative_incremental_marking_steps;
    current_.incremental_marking_bytes =
        current_.cumulative_incremental_marking_bytes -
        previous_incremental_mark_compactor_event_
            .cumulative_incremental_marking_bytes;
    current_.incremental_marking_duration =
        current_.cumulative_incremental_marking_duration -
        previous_incremental_mark_compactor_event_
            .cumulative_incremental_marking_duration;
    current_.pure_incremental_marking_duration =
        current_.cumulative_pure_incremental_marking_duration -
        previous_incremental_mark_compactor_event_
            .cumulative_pure_incremental_marking_duration;
    longest_incremental_marking_step_ = 0.0;
    incremental_mark_compactor_events_.push_front(current_);
    combined_mark_compact_speed_cache_ = 0.0;
  } else {
    DCHECK(current_.incremental_marking_bytes == 0);
    DCHECK(current_.incremental_marking_duration == 0);
    DCHECK(current_.pure_incremental_marking_duration == 0);
    longest_incremental_marking_step_ = 0.0;
    mark_compactor_events_.push_front(current_);
    combined_mark_compact_speed_cache_ = 0.0;
  }

  // TODO(ernstm): move the code below out of GCTracer.

  double duration = current_.end_time - current_.start_time;
  double spent_in_mutator = Max(current_.start_time - previous_.end_time, 0.0);

  heap_->UpdateCumulativeGCStatistics(duration, spent_in_mutator,
                                      current_.scopes[Scope::MC_MARK]);

  if (current_.type == Event::SCAVENGER && FLAG_trace_gc_ignore_scavenger)
    return;

  if (FLAG_trace_gc_nvp)
    PrintNVP();
  else
    Print();

  if (FLAG_trace_gc) {
    heap_->PrintShortHeapStatistics();
  }

  longest_incremental_marking_finalization_step_ = 0.0;
  cumulative_incremental_marking_finalization_steps_ = 0;
  cumulative_incremental_marking_finalization_duration_ = 0.0;
}


void GCTracer::SampleAllocation(double current_ms,
                                size_t new_space_counter_bytes,
                                size_t old_generation_counter_bytes) {
  if (allocation_time_ms_ == 0) {
    // It is the first sample.
    allocation_time_ms_ = current_ms;
    new_space_allocation_counter_bytes_ = new_space_counter_bytes;
    old_generation_allocation_counter_bytes_ = old_generation_counter_bytes;
    return;
  }
  // This assumes that counters are unsigned integers so that the subtraction
  // below works even if the new counter is less then the old counter.
  size_t new_space_allocated_bytes =
      new_space_counter_bytes - new_space_allocation_counter_bytes_;
  size_t old_generation_allocated_bytes =
      old_generation_counter_bytes - old_generation_allocation_counter_bytes_;
  double duration = current_ms - allocation_time_ms_;
  allocation_time_ms_ = current_ms;
  new_space_allocation_counter_bytes_ = new_space_counter_bytes;
  old_generation_allocation_counter_bytes_ = old_generation_counter_bytes;
  allocation_duration_since_gc_ += duration;
  new_space_allocation_in_bytes_since_gc_ += new_space_allocated_bytes;
  old_generation_allocation_in_bytes_since_gc_ +=
      old_generation_allocated_bytes;
}


void GCTracer::AddAllocation(double current_ms) {
  allocation_time_ms_ = current_ms;
  new_space_allocation_events_.push_front(AllocationEvent(
      allocation_duration_since_gc_, new_space_allocation_in_bytes_since_gc_));
  old_generation_allocation_events_.push_front(
      AllocationEvent(allocation_duration_since_gc_,
                      old_generation_allocation_in_bytes_since_gc_));
  allocation_duration_since_gc_ = 0;
  new_space_allocation_in_bytes_since_gc_ = 0;
  old_generation_allocation_in_bytes_since_gc_ = 0;
}


void GCTracer::AddContextDisposalTime(double time) {
  context_disposal_events_.push_front(ContextDisposalEvent(time));
}


void GCTracer::AddCompactionEvent(double duration,
                                  intptr_t live_bytes_compacted) {
  compaction_events_.push_front(
      CompactionEvent(duration, live_bytes_compacted));
}


void GCTracer::AddSurvivalRatio(double promotion_ratio) {
  survival_events_.push_front(SurvivalEvent(promotion_ratio));
}


void GCTracer::AddIncrementalMarkingStep(double duration, intptr_t bytes) {
  cumulative_incremental_marking_steps_++;
  cumulative_incremental_marking_bytes_ += bytes;
  cumulative_incremental_marking_duration_ += duration;
  longest_incremental_marking_step_ =
      Max(longest_incremental_marking_step_, duration);
  cumulative_marking_duration_ += duration;
  if (bytes > 0) {
    cumulative_pure_incremental_marking_duration_ += duration;
  }
}


void GCTracer::AddIncrementalMarkingFinalizationStep(double duration) {
  cumulative_incremental_marking_finalization_steps_++;
  cumulative_incremental_marking_finalization_duration_ += duration;
  longest_incremental_marking_finalization_step_ =
      Max(longest_incremental_marking_finalization_step_, duration);
}


void GCTracer::Output(const char* format, ...) const {
  if (FLAG_trace_gc) {
    va_list arguments;
    va_start(arguments, format);
    base::OS::VPrint(format, arguments);
    va_end(arguments);
  }

  const int kBufferSize = 256;
  char raw_buffer[kBufferSize];
  Vector<char> buffer(raw_buffer, kBufferSize);
  va_list arguments2;
  va_start(arguments2, format);
  VSNPrintF(buffer, format, arguments2);
  va_end(arguments2);

  heap_->AddToRingBuffer(buffer.start());
}


void GCTracer::Print() const {
  if (FLAG_trace_gc) {
    PrintIsolate(heap_->isolate(), "");
  }
  Output("%8.0f ms: ", heap_->isolate()->time_millis_since_init());

  Output("%s %.1f (%.1f) -> %.1f (%.1f) MB, ", current_.TypeName(false),
         static_cast<double>(current_.start_object_size) / MB,
         static_cast<double>(current_.start_memory_size) / MB,
         static_cast<double>(current_.end_object_size) / MB,
         static_cast<double>(current_.end_memory_size) / MB);

  int external_time = static_cast<int>(current_.scopes[Scope::EXTERNAL]);
  double duration = current_.end_time - current_.start_time;
  Output("%.1f / %d ms", duration, external_time);

  if (current_.type == Event::SCAVENGER) {
    if (current_.incremental_marking_steps > 0) {
      Output(" (+ %.1f ms in %d steps since last GC)",
             current_.incremental_marking_duration,
             current_.incremental_marking_steps);
    }
  } else {
    if (current_.incremental_marking_steps > 0) {
      Output(
          " (+ %.1f ms in %d steps since start of marking, "
          "biggest step %.1f ms)",
          current_.incremental_marking_duration,
          current_.incremental_marking_steps,
          current_.longest_incremental_marking_step);
    }
  }

  if (current_.gc_reason != NULL) {
    Output(" [%s]", current_.gc_reason);
  }

  if (current_.collector_reason != NULL) {
    Output(" [%s]", current_.collector_reason);
  }

  Output(".\n");
}


void GCTracer::PrintNVP() const {
  double duration = current_.end_time - current_.start_time;
  double spent_in_mutator = current_.start_time - previous_.end_time;
  intptr_t allocated_since_last_gc =
      current_.start_object_size - previous_.end_object_size;

  switch (current_.type) {
    case Event::SCAVENGER:
      PrintIsolate(heap_->isolate(),
                   "%8.0f ms: "
                   "pause=%.1f "
                   "mutator=%.1f "
                   "gc=%s "
                   "reduce_memory=%d "
                   "scavenge=%.2f "
                   "old_new=%.2f "
                   "weak=%.2f "
                   "roots=%.2f "
                   "code=%.2f "
                   "semispace=%.2f "
                   "object_groups=%.2f "
                   "steps_count=%d "
                   "steps_took=%.1f "
                   "scavenge_throughput=%" V8_PTR_PREFIX
                   "d "
                   "total_size_before=%" V8_PTR_PREFIX
                   "d "
                   "total_size_after=%" V8_PTR_PREFIX
                   "d "
                   "holes_size_before=%" V8_PTR_PREFIX
                   "d "
                   "holes_size_after=%" V8_PTR_PREFIX
                   "d "
                   "allocated=%" V8_PTR_PREFIX
                   "d "
                   "promoted=%" V8_PTR_PREFIX
                   "d "
                   "semi_space_copied=%" V8_PTR_PREFIX
                   "d "
                   "nodes_died_in_new=%d "
                   "nodes_copied_in_new=%d "
                   "nodes_promoted=%d "
                   "promotion_ratio=%.1f%% "
                   "average_survival_ratio=%.1f%% "
                   "promotion_rate=%.1f%% "
                   "semi_space_copy_rate=%.1f%% "
                   "new_space_allocation_throughput=%" V8_PTR_PREFIX
                   "d "
                   "context_disposal_rate=%.1f\n",
                   heap_->isolate()->time_millis_since_init(), duration,
                   spent_in_mutator, current_.TypeName(true),
                   current_.reduce_memory,
                   current_.scopes[Scope::SCAVENGER_SCAVENGE],
                   current_.scopes[Scope::SCAVENGER_OLD_TO_NEW_POINTERS],
                   current_.scopes[Scope::SCAVENGER_WEAK],
                   current_.scopes[Scope::SCAVENGER_ROOTS],
                   current_.scopes[Scope::SCAVENGER_CODE_FLUSH_CANDIDATES],
                   current_.scopes[Scope::SCAVENGER_SEMISPACE],
                   current_.scopes[Scope::SCAVENGER_OBJECT_GROUPS],
                   current_.incremental_marking_steps,
                   current_.incremental_marking_duration,
                   ScavengeSpeedInBytesPerMillisecond(),
                   current_.start_object_size, current_.end_object_size,
                   current_.start_holes_size, current_.end_holes_size,
                   allocated_since_last_gc, heap_->promoted_objects_size(),
                   heap_->semi_space_copied_object_size(),
                   heap_->nodes_died_in_new_space_,
                   heap_->nodes_copied_in_new_space_, heap_->nodes_promoted_,
                   heap_->promotion_ratio_, AverageSurvivalRatio(),
                   heap_->promotion_rate_, heap_->semi_space_copied_rate_,
                   NewSpaceAllocationThroughputInBytesPerMillisecond(),
                   ContextDisposalRateInMilliseconds());
      break;
    case Event::MARK_COMPACTOR:
    case Event::INCREMENTAL_MARK_COMPACTOR:
      PrintIsolate(
          heap_->isolate(),
          "%8.0f ms: "
          "pause=%.1f "
          "mutator=%.1f "
          "gc=%s "
          "reduce_memory=%d "
          "external=%.1f "
          "clear=%1.f "
          "clear.code_flush=%.1f "
          "clear.dependent_code=%.1f "
          "clear.global_handles=%.1f "
          "clear.maps=%.1f "
          "clear.slots_buffer=%.1f "
          "clear.store_buffer=%.1f "
          "clear.string_table=%.1f "
          "clear.weak_cells=%.1f "
          "clear.weak_collections=%.1f "
          "clear.weak_lists=%.1f "
          "evacuate=%.1f "
          "evacuate.candidates=%.1f "
          "evacuate.clean_up=%.1f "
          "evacuate.new_space=%.1f "
          "evacuate.update_pointers=%.1f "
          "evacuate.update_pointers.between_evacuated=%.1f "
          "evacuate.update_pointers.to_evacuated=%.1f "
          "evacuate.update_pointers.to_new=%.1f "
          "evacuate.update_pointers.weak=%.1f "
          "finish=%.1f "
          "mark=%.1f "
          "mark.finish_incremental=%.1f "
          "mark.prepare_code_flush=%.1f "
          "mark.roots=%.1f "
          "mark.weak_closure=%.1f "
          "sweep=%.1f "
          "sweep.code=%.1f "
          "sweep.map=%.1f "
          "sweep.old=%.1f "
          "incremental_finalize=%.1f "
          "steps_count=%d "
          "steps_took=%.1f "
          "longest_step=%.1f "
          "finalization_steps_count=%d "
          "finalization_steps_took=%.1f "
          "finalization_longest_step=%.1f "
          "incremental_marking_throughput=%" V8_PTR_PREFIX
          "d "
          "total_size_before=%" V8_PTR_PREFIX
          "d "
          "total_size_after=%" V8_PTR_PREFIX
          "d "
          "holes_size_before=%" V8_PTR_PREFIX
          "d "
          "holes_size_after=%" V8_PTR_PREFIX
          "d "
          "allocated=%" V8_PTR_PREFIX
          "d "
          "promoted=%" V8_PTR_PREFIX
          "d "
          "semi_space_copied=%" V8_PTR_PREFIX
          "d "
          "nodes_died_in_new=%d "
          "nodes_copied_in_new=%d "
          "nodes_promoted=%d "
          "promotion_ratio=%.1f%% "
          "average_survival_ratio=%.1f%% "
          "promotion_rate=%.1f%% "
          "semi_space_copy_rate=%.1f%% "
          "new_space_allocation_throughput=%" V8_PTR_PREFIX
          "d "
          "context_disposal_rate=%.1f "
          "compaction_speed=%" V8_PTR_PREFIX "d\n",
          heap_->isolate()->time_millis_since_init(), duration,
          spent_in_mutator, current_.TypeName(true), current_.reduce_memory,
          current_.scopes[Scope::EXTERNAL], current_.scopes[Scope::MC_CLEAR],
          current_.scopes[Scope::MC_CLEAR_CODE_FLUSH],
          current_.scopes[Scope::MC_CLEAR_DEPENDENT_CODE],
          current_.scopes[Scope::MC_CLEAR_GLOBAL_HANDLES],
          current_.scopes[Scope::MC_CLEAR_MAPS],
          current_.scopes[Scope::MC_CLEAR_SLOTS_BUFFER],
          current_.scopes[Scope::MC_CLEAR_STORE_BUFFER],
          current_.scopes[Scope::MC_CLEAR_STRING_TABLE],
          current_.scopes[Scope::MC_CLEAR_WEAK_CELLS],
          current_.scopes[Scope::MC_CLEAR_WEAK_COLLECTIONS],
          current_.scopes[Scope::MC_CLEAR_WEAK_LISTS],
          current_.scopes[Scope::MC_EVACUATE],
          current_.scopes[Scope::MC_EVACUATE_CANDIDATES],
          current_.scopes[Scope::MC_EVACUATE_CLEAN_UP],
          current_.scopes[Scope::MC_EVACUATE_NEW_SPACE],
          current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS],
          current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS_BETWEEN_EVACUATED],
          current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS_TO_EVACUATED],
          current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS_TO_NEW],
          current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS_WEAK],
          current_.scopes[Scope::MC_FINISH], current_.scopes[Scope::MC_MARK],
          current_.scopes[Scope::MC_MARK_FINISH_INCREMENTAL],
          current_.scopes[Scope::MC_MARK_PREPARE_CODE_FLUSH],
          current_.scopes[Scope::MC_MARK_ROOTS],
          current_.scopes[Scope::MC_MARK_WEAK_CLOSURE],
          current_.scopes[Scope::MC_SWEEP],
          current_.scopes[Scope::MC_SWEEP_CODE],
          current_.scopes[Scope::MC_SWEEP_MAP],
          current_.scopes[Scope::MC_SWEEP_OLD],
          current_.scopes[Scope::MC_INCREMENTAL_FINALIZE],
          current_.incremental_marking_steps,
          current_.incremental_marking_duration,
          current_.longest_incremental_marking_step,
          cumulative_incremental_marking_finalization_steps_,
          cumulative_incremental_marking_finalization_duration_,
          longest_incremental_marking_finalization_step_,
          IncrementalMarkingSpeedInBytesPerMillisecond(),
          current_.start_object_size, current_.end_object_size,
          current_.start_holes_size, current_.end_holes_size,
          allocated_since_last_gc, heap_->promoted_objects_size(),
          heap_->semi_space_copied_object_size(),
          heap_->nodes_died_in_new_space_, heap_->nodes_copied_in_new_space_,
          heap_->nodes_promoted_, heap_->promotion_ratio_,
          AverageSurvivalRatio(), heap_->promotion_rate_,
          heap_->semi_space_copied_rate_,
          NewSpaceAllocationThroughputInBytesPerMillisecond(),
          ContextDisposalRateInMilliseconds(),
          CompactionSpeedInBytesPerMillisecond());
      break;
    case Event::START:
      break;
    default:
      UNREACHABLE();
  }
}


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 (cumulative_incremental_marking_steps_ == 0) return 0.0;

  // We haven't completed an entire round of incremental marking, yet.
  // Use data from GCTracer instead of data from event buffers.
  if (incremental_mark_compactor_events_.empty()) {
    return cumulative_incremental_marking_duration_ /
           cumulative_incremental_marking_steps_;
  }

  int steps = 0;
  double durations = 0.0;
  EventBuffer::const_iterator iter = incremental_mark_compactor_events_.begin();
  while (iter != incremental_mark_compactor_events_.end()) {
    steps += iter->incremental_marking_steps;
    durations += iter->incremental_marking_duration;
    ++iter;
  }

  if (steps == 0) return 0.0;

  return durations / steps;
}


double GCTracer::MaxIncrementalMarkingDuration() const {
  // We haven't completed an entire round of incremental marking, yet.
  // Use data from GCTracer instead of data from event buffers.
  if (incremental_mark_compactor_events_.empty())
    return longest_incremental_marking_step_;

  double max_duration = 0.0;
  EventBuffer::const_iterator iter = incremental_mark_compactor_events_.begin();
  while (iter != incremental_mark_compactor_events_.end())
    max_duration = Max(iter->longest_incremental_marking_step, max_duration);

  return max_duration;
}


intptr_t GCTracer::IncrementalMarkingSpeedInBytesPerMillisecond() const {
  if (cumulative_incremental_marking_duration_ == 0.0) return 0;

  // We haven't completed an entire round of incremental marking, yet.
  // Use data from GCTracer instead of data from event buffers.
  if (incremental_mark_compactor_events_.empty()) {
    return static_cast<intptr_t>(cumulative_incremental_marking_bytes_ /
                                 cumulative_pure_incremental_marking_duration_);
  }

  intptr_t bytes = 0;
  double durations = 0.0;
  EventBuffer::const_iterator iter = incremental_mark_compactor_events_.begin();
  while (iter != incremental_mark_compactor_events_.end()) {
    bytes += iter->incremental_marking_bytes;
    durations += iter->pure_incremental_marking_duration;
    ++iter;
  }

  if (durations == 0.0) return 0;
  // Make sure the result is at least 1.
  return Max<size_t>(static_cast<size_t>(bytes / durations + 0.5), 1);
}


intptr_t GCTracer::ScavengeSpeedInBytesPerMillisecond(
    ScavengeSpeedMode mode) const {
  intptr_t bytes = 0;
  double durations = 0.0;
  EventBuffer::const_iterator iter = scavenger_events_.begin();
  while (iter != scavenger_events_.end()) {
    bytes += mode == kForAllObjects ? iter->new_space_object_size
                                    : iter->survived_new_space_object_size;
    durations += iter->end_time - iter->start_time;
    ++iter;
  }

  if (durations == 0.0) return 0;
  // Make sure the result is at least 1.
  return Max<size_t>(static_cast<size_t>(bytes / durations + 0.5), 1);
}


intptr_t GCTracer::CompactionSpeedInBytesPerMillisecond() const {
  if (compaction_events_.size() == 0) return 0;
  intptr_t bytes = 0;
  double durations = 0.0;
  CompactionEventBuffer::const_iterator iter = compaction_events_.begin();
  while (iter != compaction_events_.end()) {
    bytes += iter->live_bytes_compacted;
    durations += iter->duration;
    ++iter;
  }

  if (durations == 0.0) return 0;
  // Make sure the result is at least 1.
  return Max<intptr_t>(static_cast<intptr_t>(bytes / durations + 0.5), 1);
}


intptr_t GCTracer::MarkCompactSpeedInBytesPerMillisecond() const {
  intptr_t bytes = 0;
  double durations = 0.0;
  EventBuffer::const_iterator iter = mark_compactor_events_.begin();
  while (iter != mark_compactor_events_.end()) {
    bytes += iter->start_object_size;
    durations += iter->end_time - iter->start_time;
    ++iter;
  }

  if (durations == 0.0) return 0;
  // Make sure the result is at least 1.
  return Max<size_t>(static_cast<size_t>(bytes / durations + 0.5), 1);
}


intptr_t GCTracer::FinalIncrementalMarkCompactSpeedInBytesPerMillisecond()
    const {
  intptr_t bytes = 0;
  double durations = 0.0;
  EventBuffer::const_iterator iter = incremental_mark_compactor_events_.begin();
  while (iter != incremental_mark_compactor_events_.end()) {
    bytes += iter->start_object_size;
    durations += iter->end_time - iter->start_time;
    ++iter;
  }

  if (durations == 0.0) return 0;
  // Make sure the result is at least 1.
  return Max<size_t>(static_cast<size_t>(bytes / durations + 0.5), 1);
}


double GCTracer::CombinedMarkCompactSpeedInBytesPerMillisecond() {
  if (combined_mark_compact_speed_cache_ > 0)
    return combined_mark_compact_speed_cache_;
  const double kMinimumMarkingSpeed = 0.5;
  double speed1 =
      static_cast<double>(IncrementalMarkingSpeedInBytesPerMillisecond());
  double speed2 = static_cast<double>(
      FinalIncrementalMarkCompactSpeedInBytesPerMillisecond());
  if (speed1 < kMinimumMarkingSpeed || speed2 < kMinimumMarkingSpeed) {
    // No data for the incremental marking speed.
    // Return the non-incremental mark-compact speed.
    combined_mark_compact_speed_cache_ =
        static_cast<double>(MarkCompactSpeedInBytesPerMillisecond());
  } else {
    // Combine the speed of incremental step and the speed of the final step.
    // 1 / (1 / speed1 + 1 / speed2) = speed1 * speed2 / (speed1 + speed2).
    combined_mark_compact_speed_cache_ = speed1 * speed2 / (speed1 + speed2);
  }
  return combined_mark_compact_speed_cache_;
}


size_t GCTracer::NewSpaceAllocationThroughputInBytesPerMillisecond(
    double time_ms) const {
  size_t bytes = new_space_allocation_in_bytes_since_gc_;
  double durations = allocation_duration_since_gc_;
  AllocationEventBuffer::const_iterator iter =
      new_space_allocation_events_.begin();
  const size_t max_bytes = static_cast<size_t>(-1);
  while (iter != new_space_allocation_events_.end() &&
         bytes < max_bytes - bytes && (time_ms == 0 || durations < time_ms)) {
    bytes += iter->allocation_in_bytes_;
    durations += iter->duration_;
    ++iter;
  }

  if (durations == 0.0) return 0;
  // Make sure the result is at least 1.
  return Max<size_t>(static_cast<size_t>(bytes / durations + 0.5), 1);
}


size_t GCTracer::OldGenerationAllocationThroughputInBytesPerMillisecond(
    double time_ms) const {
  size_t bytes = old_generation_allocation_in_bytes_since_gc_;
  double durations = allocation_duration_since_gc_;
  AllocationEventBuffer::const_iterator iter =
      old_generation_allocation_events_.begin();
  const size_t max_bytes = static_cast<size_t>(-1);
  while (iter != old_generation_allocation_events_.end() &&
         bytes < max_bytes - bytes && (time_ms == 0 || durations < time_ms)) {
    bytes += iter->allocation_in_bytes_;
    durations += iter->duration_;
    ++iter;
  }

  if (durations == 0.0) return 0;
  // Make sure the result is at least 1.
  return Max<size_t>(static_cast<size_t>(bytes / durations + 0.5), 1);
}


size_t GCTracer::AllocationThroughputInBytesPerMillisecond(
    double time_ms) const {
  return NewSpaceAllocationThroughputInBytesPerMillisecond(time_ms) +
         OldGenerationAllocationThroughputInBytesPerMillisecond(time_ms);
}


size_t GCTracer::CurrentAllocationThroughputInBytesPerMillisecond() const {
  return AllocationThroughputInBytesPerMillisecond(kThroughputTimeFrameMs);
}


size_t GCTracer::CurrentOldGenerationAllocationThroughputInBytesPerMillisecond()
    const {
  return OldGenerationAllocationThroughputInBytesPerMillisecond(
      kThroughputTimeFrameMs);
}


double GCTracer::ContextDisposalRateInMilliseconds() const {
  if (context_disposal_events_.size() < kRingBufferMaxSize) return 0.0;

  double begin = heap_->MonotonicallyIncreasingTimeInMs();
  double end = 0.0;
  ContextDisposalEventBuffer::const_iterator iter =
      context_disposal_events_.begin();
  while (iter != context_disposal_events_.end()) {
    end = iter->time_;
    ++iter;
  }

  return (begin - end) / context_disposal_events_.size();
}


double GCTracer::AverageSurvivalRatio() const {
  if (survival_events_.size() == 0) return 0.0;

  double sum_of_rates = 0.0;
  SurvivalEventBuffer::const_iterator iter = survival_events_.begin();
  while (iter != survival_events_.end()) {
    sum_of_rates += iter->promotion_ratio_;
    ++iter;
  }

  return sum_of_rates / static_cast<double>(survival_events_.size());
}


bool GCTracer::SurvivalEventsRecorded() const {
  return survival_events_.size() > 0;
}


void GCTracer::ResetSurvivalEvents() { survival_events_.reset(); }
}  // namespace internal
}  // namespace v8