Adding api to get last gc object statistics for chrome://tracing.

src/api.cc

 // Copyright 2012 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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 5330 matching lines @@
                                   heap_size_limit_(0) { }
 
 
 HeapSpaceStatistics::HeapSpaceStatistics(): space_name_(0),
                                             space_size_(0),
                                             space_used_size_(0),
                                             space_available_size_(0),
                                             physical_space_size_(0) { }
 
 
+HeapObjectStatistics::HeapObjectStatistics(): object_type_(nullptr),
+                                              object_count_(0),
+                                              object_size_(0) { }
+
 bool v8::V8::InitializeICU(const char* icu_data_file) {
   return i::InitializeICU(icu_data_file);
 }
 
 
 const char* v8::V8::GetVersion() {
   return i::Version::GetVersion();
 }
 
 
@@ skipping 1553 matching lines @@
 
   space_statistics->space_name_ = heap->GetSpaceName(static_cast<int>(index));
   space_statistics->space_size_ = space->CommittedMemory();
   space_statistics->space_used_size_ = space->SizeOfObjects();
   space_statistics->space_available_size_ = space->Available();
   space_statistics->physical_space_size_ = space->CommittedPhysicalMemory();
   return true;
 }
 
 
+size_t Isolate::NumberOfHeapObjectsTypes() {
+  return i::Heap::OBJECT_STATS_COUNT;
+}

[ulan, 2015/05/06 12:46:02]

Two new-lines between functions. Please run "git cl format" to fix style.

[ssid, 2015/05/07 13:53:03]

Done.

+
+bool Isolate::GetLastGcObjectStatistics(HeapObjectStatistics* object_statistics,
+                                        size_t type_index) {
+  if (!object_statistics)
+    return false;

[ulan, 2015/05/06 12:46:02]

Either use {} or put return statements in the previous line.

[ssid, 2015/05/07 13:53:03]

Done.

+  if (type_index >= i::Heap::OBJECT_STATS_COUNT)
+    return false;
+  if (!i::FLAG_track_gc_object_stats)
+    return false;
+
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  i::Heap* heap = isolate->heap();
+  const char* object_type = heap->GetObjectTypeName(type_index);
+  size_t object_count = heap->object_count_last_gc(type_index);
+  size_t object_size = heap->object_size_last_gc(type_index);
+  if (object_type == nullptr) {

[ulan, 2015/05/06 12:46:02]

This case shouldn't be happening. Could you please post here which index has no
type?

[ssid, 2015/05/07 13:53:03]

As discussed offline, there are string categories that are not tracked/named.
So, this DCHECK helps to check if the objects are actually tracked.

+    // There should be no objects counted when the type is unknown.
+    DCHECK_EQ(object_count, 0);
+    DCHECK_EQ(object_size, 0);
+    return false;
+  }
+
+  object_statistics->object_type_ = object_type;
+  object_statistics->object_count_ = object_count;
+  object_statistics->object_size_ = object_size;
+  return true;
+}
+
+
 void Isolate::GetStackSample(const RegisterState& state, void** frames,
                              size_t frames_limit, SampleInfo* sample_info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   i::TickSample::GetStackSample(isolate, state, i::TickSample::kSkipCEntryFrame,
                                 frames, frames_limit, sample_info);
 }
 
 
 void Isolate::SetEventLogger(LogEventCallback that) {
   // Do not overwrite the event logger if we want to log explicitly.
@@ skipping 1097 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal