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perf: Write executeMount int buffer to Java in a single JNI call #58692

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perf: Write executeMount int buffer to Java in a single JNI call #58692

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25 changes: 14 additions & 11 deletions packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
#include "StateWrapperImpl.h"

#include <cxxreact/TraceSection.h>
#include <react/debug/react_native_assert.h>
#include <react/featureflags/ReactNativeFeatureFlags.h>
#include <react/jni/ReadableNativeArray.h>
#include <react/jni/ReadableNativeMap.h>
Expand Down Expand Up @@ -359,22 +360,18 @@ jni::local_ref<jobject> getProps(
}

struct InstructionBuffer {
JNIEnv* env;
jintArray ints;
std::vector<jint> ints;
jni::local_ref<jni::JArrayClass<jobject>> objects;

int intsPosition = 0;
int objectsPosition = 0;

inline void writeInt(int value) {
env->SetIntArrayRegion(ints, intsPosition, 1, &value);
intsPosition += 1;
ints.push_back(value);
}

template <size_t N>
inline void writeIntArray(const std::array<int, N>& buffer) {
env->SetIntArrayRegion(ints, intsPosition, N, buffer.data());
intsPosition += N;
ints.insert(ints.end(), buffer.begin(), buffer.end());
}

inline void writeObject(jobject obj) {
Expand Down Expand Up @@ -863,10 +860,9 @@ void FabricMountingManager::executeMount(
// Allocate the intBuffer and object array, now that we know exact sizes
// necessary
InstructionBuffer buffer = {
.env = env,
.ints = env->NewIntArray(batchMountItemIntsSize),
.objects = jni::JArrayClass<jobject>::newArray(batchMountItemObjectsSize),
};
buffer.ints.reserve(batchMountItemIntsSize);

// Fill in arrays
int prevMountItemType = -1;
Expand Down Expand Up @@ -996,6 +992,13 @@ void FabricMountingManager::executeMount(
}
}

// Copy the ints to Java in a single JNI call, rather than one per write
react_native_assert(
static_cast<int>(buffer.ints.size()) == batchMountItemIntsSize);
jintArray ints = env->NewIntArray(static_cast<jsize>(buffer.ints.size()));
env->SetIntArrayRegion(
ints, 0, static_cast<jsize>(buffer.ints.size()), buffer.ints.data());

static auto createMountItemsIntBufferBatchContainer =
JFabricUIManager::javaClassStatic()
->getMethod<jni::alias_ref<JMountItem>(
Expand All @@ -1006,7 +1009,7 @@ void FabricMountingManager::executeMount(
surfaceId,
// If there are no items, we pass a nullptr instead of passing the
// object through the JNI
batchMountItemIntsSize > 0 ? buffer.ints : nullptr,
batchMountItemIntsSize > 0 ? ints : nullptr,
batchMountItemObjectsSize > 0 ? buffer.objects.get() : nullptr,
revisionNumber);

Expand All @@ -1026,7 +1029,7 @@ void FabricMountingManager::executeMount(
telemetry.getAffectedLayoutNodesCount(),
static_cast<jboolean>(synchronous));

env->DeleteLocalRef(buffer.ints);
env->DeleteLocalRef(ints);
}

void FabricMountingManager::drainPreallocateViewsQueue() {
Expand Down
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