src: implement MemoryRetainer in Environment

This allows us to track the essentially-global objects in Environment in the heap snapshot. Note that this patch only tracks the fields that can be tracked correctly. There are still several types of fields that cannot be tracked: - v8::Data including v8::Private, v8::ObjectTemplate etc. - Internal types that do not implement MemoryRetainer yet - STL containers with MemoryRetainer* inside - STL containers with numeric types inside that should not have their nodes elided e.g. numeric keys in maps. The `BaseObject`s are now no longer globals. They are tracked as arguments in CleanupHookCallbacks referenced by the Environment node. This model is closer to how their lifetime is managed internally. To track the per-environment strong persistent properties, this patch divides them into those that are also `v8::Value` and those that are just `v8::Data`. The values can be tracked by the current memory tracker while the data cannot. This patch also implements the `MemoryRetainer` interface in several internal classes so that they can be tracked in the heap snapshot.
nodejs · joyeecheung · Mar 27, 2019 · Mar 31, 2019 · Apr 2, 2019 · Mar 31, 2019
commit 76c6bdfc77dc75425614e29df5d9b4cbe6c60f27
diff --git a/src/base_object.h b/src/base_object.h
@@ -86,7 +86,6 @@ class BaseObject : public MemoryRetainer {
 
  private:
   v8::Local<v8::Object> WrappedObject() const override;
-  bool IsRootNode() const override;
   static void DeleteMe(void* data);
 
   // persistent_handle_ needs to be at a fixed offset from the start of the

diff --git a/src/env-inl.h b/src/env-inl.h
@@ -1049,7 +1049,8 @@ void AsyncRequest::set_stopped(bool flag) {
   inline void Environment::set_ ## PropertyName(v8::Local<TypeName> value) {  \
     PropertyName ## _.Reset(isolate(), value);                                \
   }
-  ENVIRONMENT_STRONG_PERSISTENT_PROPERTIES(V)
+  ENVIRONMENT_STRONG_PERSISTENT_DATA(V)
+  ENVIRONMENT_STRONG_PERSISTENT_VALUES(V)
 #undef V
 
 }  // namespace node

diff --git a/src/env.cc b/src/env.cc
@@ -112,6 +112,28 @@ IsolateData::IsolateData(Isolate* isolate,
 #undef V
 }
 
+void IsolateData::MemoryInfo(MemoryTracker* tracker) const {
+#define V(PropertyName, StringValue)                                           \
+  tracker->TrackField(#PropertyName, PropertyName(isolate()));
+  PER_ISOLATE_SYMBOL_PROPERTIES(V)
+#undef V
+
+#define V(PropertyName, StringValue)                                           \
+  tracker->TrackField(#PropertyName, PropertyName(isolate()));
+  PER_ISOLATE_STRING_PROPERTIES(V)
+#undef V
+
+  tracker->TrackFieldWithSize(
+      "allocator", sizeof(*allocator_), "v8::ArrayBuffer::Allocator");
+  if (node_allocator_ != nullptr) {
+    tracker->TrackFieldWithSize(
+        "node_allocator", sizeof(*node_allocator_), "NodeArrayBufferAllocator");
+  }
+  tracker->TrackFieldWithSize(
+      "platform", sizeof(*platform_), "MultiIsolatePlatform");
+  // TODO(joyeecheung): implement MemoryRetainer in the option classes.
+}
+
 void InitThreadLocalOnce() {
   CHECK_EQ(0, uv_key_create(&Environment::thread_local_env));
 }
@@ -716,6 +738,7 @@ void Environment::set_debug_categories(const std::string& cats, bool enabled) {
     }
 
     DEBUG_CATEGORY_NAMES(V)
+#undef V
 
     if (comma_pos == std::string::npos)
       break;
@@ -784,6 +807,21 @@ void Environment::CollectUVExceptionInfo(Local<Value> object,
                              syscall, message, path, dest);
 }
 
+void ImmediateInfo::MemoryInfo(MemoryTracker* tracker) const {
+  tracker->TrackField("fields", fields_);
+}
+
+void TickInfo::MemoryInfo(MemoryTracker* tracker) const {
+  tracker->TrackField("fields", fields_);
+}
+
+void AsyncHooks::MemoryInfo(MemoryTracker* tracker) const {
+  tracker->TrackField("providers", providers_);
+  tracker->TrackField("async_ids_stack", async_ids_stack_);
+  tracker->TrackField("fields", fields_);
+  tracker->TrackField("async_id_fields", async_id_fields_);
+}
+
 void AsyncHooks::grow_async_ids_stack() {
   async_ids_stack_.reserve(async_ids_stack_.Length() * 3);
 
@@ -814,13 +852,70 @@ void Environment::stop_sub_worker_contexts() {
   }
 }
 
+void Environment::CleanupHookCallback::MemoryInfo(
+    MemoryTracker* tracker) const {
+  // TODO(joyeecheung): at the moment only arguments of type BaseObject will be
+  // identified and tracked here (based on their deleters),
+  // but we may convert and track other known types here.
+  BaseObject* obj = GetBaseObject();
+  if (obj != nullptr) {
+    tracker->TrackField("arg", obj);
+  }
+}
+
 void Environment::BuildEmbedderGraph(Isolate* isolate,
                                      EmbedderGraph* graph,
                                      void* data) {
   MemoryTracker tracker(isolate, graph);
-  static_cast<Environment*>(data)->ForEachBaseObject([&](BaseObject* obj) {
-    tracker.Track(obj);
-  });
+  Environment* env = static_cast<Environment*>(data);
+  tracker.Track(env);
+}
+
+inline size_t Environment::SelfSize() const {
+  size_t size = sizeof(*this);
+  // Remove non pointer fields that will be tracked in MemoryInfo()
+  // TODO(joyeecheung): refactor the MemoryTracker interface so
+  // this can be done for common types within the Track* calls automatically
+  // if a certain scope is entered.
+  size -= sizeof(thread_stopper_);
+  return size;
+}
+
+void Environment::MemoryInfo(MemoryTracker* tracker) const {
+  // Iteratable STLs have their own sizes subtracted from the parent
+  // by default.
+  tracker->TrackField("isolate_data", isolate_data_);
+  tracker->TrackField("native_modules_with_cache", native_modules_with_cache);
+  tracker->TrackField("native_modules_without_cache",
+                      native_modules_without_cache);
+  tracker->TrackField("destroy_async_id_list", destroy_async_id_list_);
+  tracker->TrackField("exec_argv", exec_argv_);
+  tracker->TrackField("should_abort_on_uncaught_toggle",
+                      should_abort_on_uncaught_toggle_);
+  tracker->TrackField("stream_base_state", stream_base_state_);
+  tracker->TrackField("fs_stats_field_array", fs_stats_field_array_);
+  tracker->TrackField("fs_stats_field_bigint_array",
+                      fs_stats_field_bigint_array_);
+  tracker->TrackField("thread_stopper", thread_stopper_);
+  tracker->TrackField("cleanup_hooks", cleanup_hooks_);
+  tracker->TrackField("async_hooks", async_hooks_);
+  tracker->TrackField("immediate_info", immediate_info_);
+  tracker->TrackField("tick_info", tick_info_);
+
+#define V(PropertyName, TypeName)                                              \
+  tracker->TrackField(#PropertyName, PropertyName());
+  ENVIRONMENT_STRONG_PERSISTENT_VALUES(V)
+#undef V
+
+  // FIXME(joyeecheung): track other fields in Environment.
+  // Currently MemoryTracker is unable to track these
+  // correctly:
+  // - Internal types that do not implement MemoryRetainer yet
+  // - STL containers with MemoryRetainer* inside
+  // - STL containers with numeric types inside that should not have their
+  //   nodes elided e.g. numeric keys in maps.
+  // We also need to make sure that when we add a non-pointer field as its own
+  // node, we shift its sizeof() size out of the Environment node.
 }
 
 char* Environment::Reallocate(char* data, size_t old_size, size_t size) {
@@ -884,8 +979,4 @@ Local<Object> BaseObject::WrappedObject() const {
   return object();
 }
 
-bool BaseObject::IsRootNode() const {
-  return !persistent_handle_.IsWeak();
-}
-
 }  // namespace node