src: cut small costs in node::MakeCallback

src/api/callback.cc

@@ -4,6 +4,8 @@
 #include "node.h"
 #include "v8.h"
 
+#include <optional>
+
 namespace node {
 
 using v8::Context;
@@ -112,9 +114,12 @@ InternalCallbackScope::InternalCallbackScope(
 
   isolate->SetIdle(false);
 
-  // The prior frame is usually undefined: no global handle then.
-  Local<Value> prior_context_frame =
-      async_context_frame::exchange(env, context_frame);
+  // The prior frame is usually undefined: no global handle then. Usually it
+  // is also the frame of the callback, and there is nothing to set.
+  Local<Value> prior_context_frame = async_context_frame::current(isolate);
+  if (prior_context_frame != context_frame) {
+    async_context_frame::set(env, context_frame);
+  }
   if (!prior_context_frame->IsUndefined()) {
     prior_context_frame_.Reset(isolate, prior_context_frame);
   }
@@ -349,7 +354,14 @@ MaybeLocal<Value> InternalMakeCallback(Isolate* isolate,
   }
   Environment* env = Environment::GetCurrent(context);
   CHECK_NOT_NULL(env);
-  Context::Scope context_scope(env->context());
+  // Entering the context changes nothing when it is already the entered and
+  // the current one, which is the common case for addons.
+  Local<Context> env_context = env->context();
+  std::optional<Context::Scope> context_scope;
+  if (isolate->GetEnteredOrMicrotaskContext() != env_context ||
+      isolate->GetCurrentContext() != env_context) {
+    context_scope.emplace(env_context);
+  }
   MaybeLocal<Value> ret = InternalMakeCallback(
       env, recv, recv, callback, argc, argv, asyncContext, context_frame);
   if (ret.IsEmpty() && env->async_callback_scope_depth() == 0) {

src/env.cc

@@ -133,7 +133,7 @@ void Environment::ResetPromiseHooks(Local<Function> init,
 void AsyncHooks::push_async_context(
     double async_id,
     double trigger_async_id,
-    std::variant<Local<Object>*, Global<Object>*> resource) {
+    const std::variant<Local<Object>*, Global<Object>*>& resource) {
   std::visit([](auto* ptr) { CHECK_IMPLIES(ptr != nullptr, !ptr->IsEmpty()); },
              resource);
 
@@ -161,9 +161,13 @@ void AsyncHooks::push_async_context(
   // False positive: https://github.com/cpplint/cpplint/issues/410
   // NOLINTNEXTLINE(whitespace/newline)
   if (std::visit([](auto* ptr) { return ptr != nullptr; }, resource)) {
-    native_execution_async_resources_.resize(offset + 1);
     // Caveat: This is a v8::Local<>* assignment, we do not keep a v8::Global<>!
-    native_execution_async_resources_[offset] = resource;
+    if (native_execution_async_resources_.size() == offset) {
+      native_execution_async_resources_.push_back(resource);
+    } else {
+      native_execution_async_resources_.resize(offset + 1);
+      native_execution_async_resources_[offset] = resource;
+    }
   }
 }
 
@@ -196,7 +200,11 @@ bool AsyncHooks::pop_async_context(double async_id) {
                  native_execution_async_resources_[i]);
     }
 #endif
-    native_execution_async_resources_.resize(offset);
+    if (native_execution_async_resources_.size() == offset + 1) {
+      native_execution_async_resources_.pop_back();
+    } else {
+      native_execution_async_resources_.resize(offset);
+    }
     native_execution_async_resources_.shrink_to_fit();
   }
 

src/env.h

@@ -427,7 +427,7 @@ class AsyncHooks : public MemoryRetainer {
   void push_async_context(
       double async_id,
       double trigger_async_id,
-      std::variant<v8::Local<v8::Object>*, v8::Global<v8::Object>*>
+      const std::variant<v8::Local<v8::Object>*, v8::Global<v8::Object>*>&
           execution_async_resource);
   bool pop_async_context(double async_id);
   void clear_async_id_stack();  // Used in fatal exceptions.