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.

PR-URL: #27018
Refs: #26776
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

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
@@ -95,7 +94,7 @@ class BaseObject : public MemoryRetainer {
   // position of members in memory are predictable. For more information please
   // refer to `doc/guides/node-postmortem-support.md`
   friend int GenDebugSymbols();
-  friend class Environment;
+  friend class CleanupHookCallback;
 
   Persistent<v8::Object> persistent_handle_;
   Environment* env_;

src/env-inl.h

@@ -980,17 +980,17 @@ void Environment::RemoveCleanupHook(void (*fn)(void*), void* arg) {
   cleanup_hooks_.erase(search);
 }
 
-size_t Environment::CleanupHookCallback::Hash::operator()(
+size_t CleanupHookCallback::Hash::operator()(
     const CleanupHookCallback& cb) const {
   return std::hash<void*>()(cb.arg_);
 }
 
-bool Environment::CleanupHookCallback::Equal::operator()(
+bool CleanupHookCallback::Equal::operator()(
     const CleanupHookCallback& a, const CleanupHookCallback& b) const {
   return a.fn_ == b.fn_ && a.arg_ == b.arg_;
 }
 
-BaseObject* Environment::CleanupHookCallback::GetBaseObject() const {
+BaseObject* CleanupHookCallback::GetBaseObject() const {
   if (fn_ == BaseObject::DeleteMe)
     return static_cast<BaseObject*>(arg_);
   else
@@ -1054,6 +1054,7 @@ void AsyncRequest::set_stopped(bool flag) {
     PropertyName ## _.Reset(isolate(), value);                                \
   }
   ENVIRONMENT_STRONG_PERSISTENT_PROPERTIES(V)
+  ENVIRONMENT_STRONG_PERSISTENT_VALUES(V)
 #undef V
 
 }  // namespace node

src/env.cc

@@ -112,6 +112,29 @@ 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
+
+  if (node_allocator_ != nullptr) {
+    tracker->TrackFieldWithSize(
+        "node_allocator", sizeof(*node_allocator_), "NodeArrayBufferAllocator");
+  } else {
+    tracker->TrackFieldWithSize(
+        "allocator", sizeof(*allocator_), "v8::ArrayBuffer::Allocator");
+  }
+  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));
 }
@@ -707,6 +730,7 @@ void Environment::set_debug_categories(const std::string& cats, bool enabled) {
     }
 
     DEBUG_CATEGORY_NAMES(V)
+#undef V
 
     if (comma_pos == std::string::npos)
       break;
@@ -775,6 +799,21 @@ 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);
 
@@ -805,13 +844,83 @@ void Environment::stop_sub_worker_contexts() {
   }
 }
 
+void MemoryTracker::TrackField(const char* edge_name,
+                               const CleanupHookCallback& value,
+                               const char* node_name) {
+  v8::HandleScope handle_scope(isolate_);
+  // Here, we utilize the fact that CleanupHookCallback instances
+  // are all unique and won't be tracked twice in one BuildEmbedderGraph
+  // callback.
+  MemoryRetainerNode* n =
+      PushNode("CleanupHookCallback", sizeof(value), edge_name);
+  // 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 = value.GetBaseObject();
+  if (obj != nullptr) {
+    this->TrackField("arg", obj);
+  }
+  CHECK_EQ(CurrentNode(), n);
+  CHECK_NE(n->size_, 0);
+  PopNode();
+}
+
 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_);
+  size -= sizeof(async_hooks_);
+  size -= sizeof(tick_info_);
+  size -= sizeof(immediate_info_);
+  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) {
@@ -875,8 +984,4 @@ Local<Object> BaseObject::WrappedObject() const {
   return object();
 }
 
-bool BaseObject::IsRootNode() const {
-  return !persistent_handle_.IsWeak();
-}
-
 }  // namespace node