perf: Speed up Dispatcher get calls

mrousavy · Jun 23, 2024 · a6b69b3 · a6b69b3
1 parent f4ad208
commit a6b69b3
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diff --git a/packages/react-native-nitro-modules/cpp/threading/Dispatcher.cpp b/packages/react-native-nitro-modules/cpp/threading/Dispatcher.cpp
@@ -7,15 +7,31 @@ using namespace facebook;
 
 static constexpr auto GLOBAL_DISPATCHER_HOLDER_NAME = "__nitroDispatcher";
 
+std::unordered_map<jsi::Runtime*, std::weak_ptr<Dispatcher>> Dispatcher::_globalCache;
+
 void Dispatcher::installRuntimeGlobalDispatcher(jsi::Runtime& runtime, std::shared_ptr<Dispatcher> dispatcher) {
   Logger::log(TAG, "Installing global Dispatcher Holder...");
+
+  // Store a weak reference in global cache
+  _globalCache[&runtime] = std::weak_ptr(dispatcher);
 
+  // Inject the dispatcher into Runtime global (runtime will hold a strong reference)
   jsi::Object dispatcherHolder(runtime);
   dispatcherHolder.setNativeState(runtime, dispatcher);
   runtime.global().setProperty(runtime, GLOBAL_DISPATCHER_HOLDER_NAME, dispatcherHolder);
 }
 
 std::shared_ptr<Dispatcher> Dispatcher::getRuntimeGlobalDispatcher(jsi::Runtime& runtime) {
+  if (_globalCache.contains(&runtime)) [[likely]] {
+    // the runtime is known - we have something in cache
+    std::weak_ptr<Dispatcher> weakDispatcher = _globalCache[&runtime];
+    std::shared_ptr<Dispatcher> strongDispatcher = weakDispatcher.lock();
+    if (strongDispatcher) {
+      // the weak reference we cached is still valid - return it!
+      return strongDispatcher;
+    }
+  }
+
   jsi::Value dispatcherHolderValue = getRuntimeGlobalDispatcherHolder(runtime);
   jsi::Object dispatcherHolder = dispatcherHolderValue.getObject(runtime);
   return dispatcherHolder.getNativeState<Dispatcher>(runtime);

diff --git a/packages/react-native-nitro-modules/cpp/threading/Dispatcher.hpp b/packages/react-native-nitro-modules/cpp/threading/Dispatcher.hpp
@@ -70,6 +70,9 @@ class Dispatcher : public jsi::NativeState {
     // 3. Return an open future that gets resolved later by the dispatcher Thread
     return future;
   }
+
+private:
+  static std::unordered_map<jsi::Runtime*, std::weak_ptr<Dispatcher>> _globalCache;
 
 private:
   static constexpr auto TAG = "Dispatcher";