src: include Environment in snapshot

This snapshots a lot more data for startup than what we did previously
for increased startup performance.

                                                                                       confidence improvement accuracy (*)   (**)  (***)
    misc/startup.js mode='process' script='benchmark/fixtures/require-cachable' dur=1        ***      9.73 %       ±3.78% ±5.03% ±6.54%
    misc/startup.js mode='process' script='test/fixtures/semicolon' dur=1                    ***     36.11 %       ±3.91% ±5.23% ±6.86%

Author: addaleax

node.gyp

@@ -1157,6 +1157,7 @@
         'test/cctest/test_per_process.cc',
         'test/cctest/test_platform.cc',
         'test/cctest/test_json_utils.cc',
+        'test/cctest/test_snapshot_support.cc',
         'test/cctest/test_sockaddr.cc',
         'test/cctest/test_traced_value.cc',
         'test/cctest/test_util.cc',

src/aliased_buffer.h

@@ -4,6 +4,8 @@
 #if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 
 #include <cinttypes>
+// TODO(addaleax): There really, really should be an aliased_buffer-inl.h.
+#include "snapshot_support-inl.h"
 #include "util-inl.h"
 #include "v8.h"
 
@@ -30,8 +32,10 @@ template <class NativeT,
           class V8T,
           // SFINAE NativeT to be scalar
           typename = std::enable_if_t<std::is_scalar<NativeT>::value>>
-class AliasedBufferBase {
+class AliasedBufferBase final : public Snapshottable {
  public:
+  AliasedBufferBase() {}
+
   AliasedBufferBase(v8::Isolate* isolate, const size_t count)
       : isolate_(isolate), count_(count), byte_offset_(0) {
     CHECK_GT(count, 0);
@@ -243,11 +247,45 @@ class AliasedBufferBase {
     count_ = new_capacity;
   }
 
+  void Serialize(SnapshotCreateData* snapshot_data) const override {
+    v8::HandleScope handle_scope(isolate_);
+    snapshot_data->StartWriteEntry("AliasedBuffer");
+    snapshot_data->WriteUint64(count_);
+    snapshot_data->WriteUint64(byte_offset_);
+    v8::Local<V8T> arr = GetJSArray();
+    snapshot_data->WriteObject(arr->CreationContext(), arr);
+    snapshot_data->EndWriteEntry();
+  }
+
+  AliasedBufferBase(v8::Local<v8::Context> context,
+                    SnapshotReadData* snapshot_data)
+      : isolate_(context->GetIsolate()) {
+    v8::HandleScope handle_scope(isolate_);
+    uint64_t count, byte_offset;
+    if (snapshot_data->StartReadEntry("AliasedBuffer").IsNothing() ||
+        !snapshot_data->ReadUint64().To(&count) ||
+        !snapshot_data->ReadUint64().To(&byte_offset)) {
+      return;
+    }
+
+    count_ = count;
+    byte_offset_ = byte_offset;
+
+    v8::Local<V8T> field;
+    if (!snapshot_data->ReadObject<V8T>(context).To(&field)) return;
+    js_array_.Reset(isolate_, field);
+    buffer_ = reinterpret_cast<NativeT*>(static_cast<char*>(
+        field->Buffer()->GetBackingStore()->Data()) +
+        byte_offset_);
+
+    snapshot_data->EndReadEntry();
+  }
+
  private:
-  v8::Isolate* isolate_;
-  size_t count_;
-  size_t byte_offset_;
-  NativeT* buffer_;
+  v8::Isolate* isolate_ = nullptr;
+  size_t count_ = 0;
+  size_t byte_offset_ = 0;
+  NativeT* buffer_ = nullptr;
   v8::Global<V8T> js_array_;
 };
 

src/api/environment.cc

@@ -5,6 +5,7 @@
 #include "node_native_module_env.h"
 #include "node_platform.h"
 #include "node_v8_platform-inl.h"
+#include "snapshot_support-inl.h"
 #include "uv.h"
 
 #if HAVE_INSPECTOR
@@ -390,6 +391,12 @@ Environment* CreateEnvironment(
     env->set_abort_on_uncaught_exception(false);
   }
 
+  if (isolate_data->snapshot_data() != nullptr &&
+      !isolate_data->snapshot_data()->errors().empty()) {
+    FreeEnvironment(env);
+    return nullptr;
+  }
+
 #if HAVE_INSPECTOR
   if (inspector_parent_handle) {
     env->InitializeInspector(
@@ -400,7 +407,8 @@ Environment* CreateEnvironment(
   }
 #endif
 
-  if (env->RunBootstrapping().IsEmpty()) {
+  if (env->isolate_data()->snapshot_data() == nullptr &&
+      env->RunBootstrapping().IsEmpty()) {
     FreeEnvironment(env);
     return nullptr;
   }

src/base_object-inl.h

@@ -101,6 +101,7 @@ Environment* BaseObject::env() const {
 }
 
 BaseObject* BaseObject::FromJSObject(v8::Local<v8::Value> value) {
+  DCHECK(value->IsObject());
   v8::Local<v8::Object> obj = value.As<v8::Object>();
   DCHECK_GE(obj->InternalFieldCount(), BaseObject::kSlot);
   return static_cast<BaseObject*>(

src/base_object.h

@@ -25,6 +25,7 @@
 #if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 
 #include "memory_tracker.h"
+#include "snapshot_support.h"
 #include "v8.h"
 #include <type_traits>  // std::remove_reference
 
@@ -34,7 +35,7 @@ class Environment;
 template <typename T, bool kIsWeak>
 class BaseObjectPtrImpl;
 
-class BaseObject : public MemoryRetainer {
+class BaseObject : public MemoryRetainer, public Snapshottable {
  public:
   enum InternalFields { kSlot, kInternalFieldCount };
 
@@ -101,6 +102,11 @@ class BaseObject : public MemoryRetainer {
   static v8::Local<v8::FunctionTemplate> GetConstructorTemplate(
       Environment* env);
 
+  static v8::StartupData SerializeInternalFields(
+      v8::Local<v8::Object> object, int index, void* data);
+  virtual v8::StartupData SerializeInternalFields(
+      int index, SnapshotCreateData* snapshot_data) const;
+
  protected:
   virtual inline void OnGCCollect();
 

src/env-inl.h

@@ -73,33 +73,14 @@ inline worker::Worker* IsolateData::worker_context() const {
   return worker_context_;
 }
 
+SnapshotReadData* IsolateData::snapshot_data() const {
+  return snapshot_data_;
+}
+
 inline v8::Local<v8::String> IsolateData::async_wrap_provider(int index) const {
   return async_wrap_providers_[index].Get(isolate_);
 }
 
-inline AsyncHooks::AsyncHooks()
-    : async_ids_stack_(env()->isolate(), 16 * 2),
-      fields_(env()->isolate(), kFieldsCount),
-      async_id_fields_(env()->isolate(), kUidFieldsCount) {
-  clear_async_id_stack();
-
-  // Always perform async_hooks checks, not just when async_hooks is enabled.
-  // TODO(AndreasMadsen): Consider removing this for LTS releases.
-  // See discussion in https://github.com/nodejs/node/pull/15454
-  // When removing this, do it by reverting the commit. Otherwise the test
-  // and flag changes won't be included.
-  fields_[kCheck] = 1;
-
-  // kDefaultTriggerAsyncId should be -1, this indicates that there is no
-  // specified default value and it should fallback to the executionAsyncId.
-  // 0 is not used as the magic value, because that indicates a missing context
-  // which is different from a default context.
-  async_id_fields_[AsyncHooks::kDefaultTriggerAsyncId] = -1;
-
-  // kAsyncIdCounter should start at 1 because that'll be the id the execution
-  // context during bootstrap (code that runs before entering uv_run()).
-  async_id_fields_[AsyncHooks::kAsyncIdCounter] = 1;
-}
 inline AliasedUint32Array& AsyncHooks::fields() {
   return fields_;
 }
@@ -128,6 +109,10 @@ inline Environment* AsyncHooks::env() {
   return Environment::ForAsyncHooks(this);
 }
 
+inline const Environment* AsyncHooks::env() const {
+  return Environment::ForAsyncHooks(const_cast<AsyncHooks*>(this));
+}
+
 // Remember to keep this code aligned with pushAsyncContext() in JS.
 inline void AsyncHooks::push_async_context(double async_id,
                                            double trigger_async_id,
@@ -238,9 +223,6 @@ inline void Environment::PopAsyncCallbackScope() {
   async_callback_scope_depth_--;
 }
 
-inline ImmediateInfo::ImmediateInfo(v8::Isolate* isolate)
-    : fields_(isolate, kFieldsCount) {}
-
 inline AliasedUint32Array& ImmediateInfo::fields() {
   return fields_;
 }
@@ -265,9 +247,6 @@ inline void ImmediateInfo::ref_count_dec(uint32_t decrement) {
   fields_[kRefCount] -= decrement;
 }
 
-inline TickInfo::TickInfo(v8::Isolate* isolate)
-    : fields_(isolate, kFieldsCount) {}
-
 inline AliasedUint8Array& TickInfo::fields() {
   return fields_;
 }
@@ -467,15 +446,27 @@ inline void Environment::set_is_in_inspector_console_call(bool value) {
 }
 #endif
 
+inline const AsyncHooks* Environment::async_hooks() const {
+  return &async_hooks_;
+}
+
 inline AsyncHooks* Environment::async_hooks() {
   return &async_hooks_;
 }
 
+inline const ImmediateInfo* Environment::immediate_info() const {
+  return &immediate_info_;
+}
+
 inline ImmediateInfo* Environment::immediate_info() {
   return &immediate_info_;
 }
 
-inline TickInfo* Environment::tick_info() {
+inline const TickInfo* Environment::tick_info() const {
+  return &tick_info_;
+}
+
+inline TickInfo* Environment::tick_info()  {
   return &tick_info_;
 }
 
@@ -926,6 +917,10 @@ inline performance::PerformanceState* Environment::performance_state() {
   return performance_state_.get();
 }
 
+const performance::PerformanceState* Environment::performance_state() const {
+  return performance_state_.get();
+}
+
 inline std::unordered_map<std::string, uint64_t>*
     Environment::performance_marks() {
   return &performance_marks_;
@@ -1213,7 +1208,7 @@ BaseObject* CleanupHookCallback::GetBaseObject() const {
 }
 
 template <typename T>
-void Environment::ForEachBaseObject(T&& iterator) {
+void Environment::ForEachBaseObject(T&& iterator) const {
   for (const auto& hook : cleanup_hooks_) {
     BaseObject* obj = hook.GetBaseObject();
     if (obj != nullptr)