[heap] Provide the number of native and detached context via Heap API.

This adds two fields to the HeapStatistics struct:
- number_of_native_contexts,
- number_of_detached_contexts.

Bug: chromium:793789
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: If6942a97fd22a9e70781eed2aa286aba4c0e7f70
Reviewed-on: https://chromium-review.googlesource.com/819730
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50007}

include/v8.h

@@ -6508,6 +6508,8 @@ class V8_EXPORT HeapStatistics {
   size_t heap_size_limit() { return heap_size_limit_; }
   size_t malloced_memory() { return malloced_memory_; }
   size_t peak_malloced_memory() { return peak_malloced_memory_; }
+  size_t number_of_native_contexts() { return number_of_native_contexts_; }
+  size_t number_of_detached_contexts() { return number_of_detached_contexts_; }
 
   /**
    * Returns a 0/1 boolean, which signifies whether the V8 overwrite heap
@@ -6525,6 +6527,8 @@ class V8_EXPORT HeapStatistics {
   size_t malloced_memory_;
   size_t peak_malloced_memory_;
   bool does_zap_garbage_;
+  size_t number_of_native_contexts_;
+  size_t number_of_detached_contexts_;
 
   friend class V8;
   friend class Isolate;

src/api.cc

@@ -6445,7 +6445,9 @@ HeapStatistics::HeapStatistics()
       heap_size_limit_(0),
       malloced_memory_(0),
       peak_malloced_memory_(0),
-      does_zap_garbage_(0) {}
+      does_zap_garbage_(0),
+      number_of_native_contexts_(0),
+      number_of_detached_contexts_(0) {}
 
 HeapSpaceStatistics::HeapSpaceStatistics(): space_name_(0),
                                             space_size_(0),
@@ -8792,6 +8794,9 @@ void Isolate::GetHeapStatistics(HeapStatistics* heap_statistics) {
       isolate->allocator()->GetCurrentMemoryUsage();
   heap_statistics->peak_malloced_memory_ =
       isolate->allocator()->GetMaxMemoryUsage();
+  heap_statistics->number_of_native_contexts_ = heap->NumberOfNativeContexts();
+  heap_statistics->number_of_detached_contexts_ =
+      heap->NumberOfDetachedContexts();
   heap_statistics->does_zap_garbage_ = heap->ShouldZapGarbage();
 }
 

src/heap/heap.cc

@@ -6526,6 +6526,22 @@ bool Heap::GetObjectTypeName(size_t index, const char** object_type,
   return false;
 }
 
+size_t Heap::NumberOfNativeContexts() {
+  int result = 0;
+  Object* context = native_contexts_list();
+  while (!context->IsUndefined(isolate())) {
+    ++result;
+    Context* native_context = Context::cast(context);
+    context = native_context->next_context_link();
+  }
+  return result;
+}
+
+size_t Heap::NumberOfDetachedContexts() {
+  // The detached_contexts() array has two entries per detached context.
+  return detached_contexts()->length() / 2;
+}
+
 const char* AllocationSpaceName(AllocationSpace space) {
   switch (space) {
     case NEW_SPACE:

src/heap/heap.h

@@ -1366,6 +1366,12 @@ class Heap {
   bool GetObjectTypeName(size_t index, const char** object_type,
                          const char** object_sub_type);
 
+  // The total number of native contexts object on the heap.
+  size_t NumberOfNativeContexts();
+  // The total number of native contexts that were detached but were not
+  // garbage collected yet.
+  size_t NumberOfDetachedContexts();
+
   // ===========================================================================
   // Code statistics. ==========================================================
   // ===========================================================================

test/cctest/test-api.cc

@@ -18467,7 +18467,6 @@ TEST(SetStackLimitInThread) {
   }
 }
 
-
 THREADED_TEST(GetHeapStatistics) {
   LocalContext c1;
   v8::HandleScope scope(c1->GetIsolate());
@@ -18479,6 +18478,55 @@ THREADED_TEST(GetHeapStatistics) {
   CHECK_NE(static_cast<int>(heap_statistics.used_heap_size()), 0);
 }
 
+TEST(NumberOfNativeContexts) {
+  static const size_t kNumTestContexts = 10;
+  i::Isolate* isolate = CcTest::i_isolate();
+  i::HandleScope scope(isolate);
+  v8::Global<v8::Context> context[kNumTestContexts];
+  v8::HeapStatistics heap_statistics;
+  CHECK_EQ(0u, heap_statistics.number_of_native_contexts());
+  CcTest::isolate()->GetHeapStatistics(&heap_statistics);
+  CHECK_EQ(0u, heap_statistics.number_of_native_contexts());
+  for (size_t i = 0; i < kNumTestContexts; i++) {
+    i::HandleScope inner(isolate);
+    context[i].Reset(CcTest::isolate(), v8::Context::New(CcTest::isolate()));
+    CcTest::isolate()->GetHeapStatistics(&heap_statistics);
+    CHECK_EQ(i + 1, heap_statistics.number_of_native_contexts());
+  }
+  for (size_t i = 0; i < kNumTestContexts; i++) {
+    context[i].Reset();
+    CcTest::CollectAllGarbage(i::Heap::kAbortIncrementalMarkingMask);
+    CcTest::isolate()->GetHeapStatistics(&heap_statistics);
+    CHECK_EQ(kNumTestContexts - i - 1u,
+             heap_statistics.number_of_native_contexts());
+  }
+}
+
+TEST(NumberOfDetachedContexts) {
+  static const size_t kNumTestContexts = 10;
+  i::Isolate* isolate = CcTest::i_isolate();
+  i::HandleScope scope(isolate);
+  v8::Global<v8::Context> context[kNumTestContexts];
+  v8::HeapStatistics heap_statistics;
+  CHECK_EQ(0u, heap_statistics.number_of_detached_contexts());
+  CcTest::isolate()->GetHeapStatistics(&heap_statistics);
+  CHECK_EQ(0u, heap_statistics.number_of_detached_contexts());
+  for (size_t i = 0; i < kNumTestContexts; i++) {
+    i::HandleScope inner(isolate);
+    v8::Local<v8::Context> local = v8::Context::New(CcTest::isolate());
+    context[i].Reset(CcTest::isolate(), local);
+    local->DetachGlobal();
+    CcTest::isolate()->GetHeapStatistics(&heap_statistics);
+    CHECK_EQ(i + 1, heap_statistics.number_of_detached_contexts());
+  }
+  for (size_t i = 0; i < kNumTestContexts; i++) {
+    context[i].Reset();
+    CcTest::CollectAllGarbage(i::Heap::kAbortIncrementalMarkingMask);
+    CcTest::isolate()->GetHeapStatistics(&heap_statistics);
+    CHECK_EQ(kNumTestContexts - i - 1u,
+             heap_statistics.number_of_detached_contexts());
+  }
+}
 
 class VisitorImpl : public v8::ExternalResourceVisitor {
  public: