Create feature flag to make estimation for remaining time in frame fo…

…r view preallocation more precise (#46563)

Summary:
Pull Request resolved: #46563

Changelog: [internal]

Our current implementation of view preallocation on Android runs very early in the frame (during the `animation` stage, after `input` and before `traversal`). In that implementation, we check the remaining time in the frame and we allocate half of that time for view preallocation.

This logic can make us drop frames unnecessarily, if the work that we need to do after this allocated time is longer than we expect. Because we don't know how long the `traversal` stage will be, we don't account for that time at all (or, at best, we do only use half of the remaining time).

This creates a feature flag to move view preallocation outside of the choreographer, so we can compute the remaining time considering all the work we did in the frame, and not just the work we did in the input stage.

Reviewed By: javache

Differential Revision: D62962341

fbshipit-source-id: 69aaeecc8596906e61b47af9adad23c1075a091a

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/MountItemDispatcher.java

@@ -21,6 +21,7 @@
 import com.facebook.react.bridge.ReactNoCrashSoftException;
 import com.facebook.react.bridge.ReactSoftExceptionLogger;
 import com.facebook.react.bridge.RetryableMountingLayerException;
+import com.facebook.react.bridge.UiThreadUtil;
 import com.facebook.react.fabric.mounting.mountitems.DispatchCommandMountItem;
 import com.facebook.react.fabric.mounting.mountitems.MountItem;
 import com.facebook.react.internal.featureflags.ReactNativeFeatureFlags;
@@ -54,6 +55,21 @@ public class MountItemDispatcher {
   private long mBatchedExecutionTime = 0L;
   private long mRunStartTime = 0L;
 
+  private long mLastFrameTimeNanos = 0L;
+  private boolean mIsPremountScheduled = false;
+  private final Runnable mPremountRunnable =
+      () -> {
+        mIsPremountScheduled = false;
+
+        if (mPreMountItems.isEmpty()) {
+          // Avoid starting systrace if there are no pre mount items.
+          return;
+        }
+
+        long deadline = mLastFrameTimeNanos + (FRAME_TIME_NS / 2);
+        dispatchPreMountItemsImpl(deadline);
+      };
+
   public MountItemDispatcher(MountingManager mountingManager, ItemDispatchListener listener) {
     mMountingManager = mountingManager;
     mItemDispatchListener = listener;
@@ -338,22 +354,35 @@ private boolean dispatchMountItems() {
   @UiThread
   @ThreadConfined(UI)
   public void dispatchPreMountItems(long frameTimeNanos) {
+    mLastFrameTimeNanos = frameTimeNanos;
+
     if (mPreMountItems.isEmpty()) {
       // Avoid starting systrace if there are no pre mount items.
       return;
     }
 
+    if (ReactNativeFeatureFlags.enablePreciseSchedulingForPremountItemsOnAndroid()) {
+      if (!mIsPremountScheduled) {
+        mIsPremountScheduled = true;
+        UiThreadUtil.getUiThreadHandler().post(mPremountRunnable);
+      }
+    } else {
+      long deadline = mLastFrameTimeNanos + FRAME_TIME_NS / 2;
+      dispatchPreMountItemsImpl(deadline);
+    }
+  }
+
+  private void dispatchPreMountItemsImpl(long deadline) {
     Systrace.beginSection(
         Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, "MountItemDispatcher::premountViews");
 
     // dispatchPreMountItems cannot be reentrant, but we want to prevent dispatchMountItems from
     // reentering during dispatchPreMountItems
     mInDispatch = true;
 
-    long frameTimeDeadline = frameTimeNanos + FRAME_TIME_NS / 2;
     try {
       while (true) {
-        if (System.nanoTime() > frameTimeDeadline) {
+        if (System.nanoTime() > deadline) {
           break;
         }
 

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlags.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<60fcb02736ca814a842225291e3a55b1>>
+ * @generated SignedSource<<73409b567e77f17838ae9681a8e20be6>>
  */
 
 /**
@@ -148,6 +148,12 @@ public object ReactNativeFeatureFlags {
   @JvmStatic
   public fun enableMicrotasks(): Boolean = accessor.enableMicrotasks()
 
+  /**
+   * Moves execution of pre-mount items to outside the choregrapher in the main thread, so we can estimate idle time more precisely (Android only).
+   */
+  @JvmStatic
+  public fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean = accessor.enablePreciseSchedulingForPremountItemsOnAndroid()
+
   /**
    * When enabled, Android will receive prop updates based on the differences between the last rendered shadow node and the last committed shadow node.
    */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxAccessor.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<f2a64fef9775f1890adcf3d761061182>>
+ * @generated SignedSource<<9f2978b5a732a3ca4f3c3d74debba782>>
  */
 
 /**
@@ -40,6 +40,7 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
   private var enableLayoutAnimationsOnIOSCache: Boolean? = null
   private var enableLongTaskAPICache: Boolean? = null
   private var enableMicrotasksCache: Boolean? = null
+  private var enablePreciseSchedulingForPremountItemsOnAndroidCache: Boolean? = null
   private var enablePropsUpdateReconciliationAndroidCache: Boolean? = null
   private var enableReportEventPaintTimeCache: Boolean? = null
   private var enableSynchronousStateUpdatesCache: Boolean? = null
@@ -251,6 +252,15 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
     return cached
   }
 
+  override fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean {
+    var cached = enablePreciseSchedulingForPremountItemsOnAndroidCache
+    if (cached == null) {
+      cached = ReactNativeFeatureFlagsCxxInterop.enablePreciseSchedulingForPremountItemsOnAndroid()
+      enablePreciseSchedulingForPremountItemsOnAndroidCache = cached
+    }
+    return cached
+  }
+
   override fun enablePropsUpdateReconciliationAndroid(): Boolean {
     var cached = enablePropsUpdateReconciliationAndroidCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxInterop.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<03618f182004add50655a88e6e65e96d>>
+ * @generated SignedSource<<0d2f5427661ce67e468aea47bdd29802>>
  */
 
 /**
@@ -68,6 +68,8 @@ public object ReactNativeFeatureFlagsCxxInterop {
 
   @DoNotStrip @JvmStatic public external fun enableMicrotasks(): Boolean
 
+  @DoNotStrip @JvmStatic public external fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean
+
   @DoNotStrip @JvmStatic public external fun enablePropsUpdateReconciliationAndroid(): Boolean
 
   @DoNotStrip @JvmStatic public external fun enableReportEventPaintTime(): Boolean

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsDefaults.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<fc795741e932cf24e5bfb7e2fe1046ae>>
+ * @generated SignedSource<<72e3e7b5a53e64f8f48310d8b07cdf76>>
  */
 
 /**
@@ -63,6 +63,8 @@ public open class ReactNativeFeatureFlagsDefaults : ReactNativeFeatureFlagsProvi
 
   override fun enableMicrotasks(): Boolean = false
 
+  override fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean = false
+
   override fun enablePropsUpdateReconciliationAndroid(): Boolean = false
 
   override fun enableReportEventPaintTime(): Boolean = false

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsLocalAccessor.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<0dbb1f1a08649132955698ac51050e62>>
+ * @generated SignedSource<<e1a44f8e54709e70934f1d418d4ed80f>>
  */
 
 /**
@@ -44,6 +44,7 @@ public class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcces
   private var enableLayoutAnimationsOnIOSCache: Boolean? = null
   private var enableLongTaskAPICache: Boolean? = null
   private var enableMicrotasksCache: Boolean? = null
+  private var enablePreciseSchedulingForPremountItemsOnAndroidCache: Boolean? = null
   private var enablePropsUpdateReconciliationAndroidCache: Boolean? = null
   private var enableReportEventPaintTimeCache: Boolean? = null
   private var enableSynchronousStateUpdatesCache: Boolean? = null
@@ -275,6 +276,16 @@ public class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcces
     return cached
   }
 
+  override fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean {
+    var cached = enablePreciseSchedulingForPremountItemsOnAndroidCache
+    if (cached == null) {
+      cached = currentProvider.enablePreciseSchedulingForPremountItemsOnAndroid()
+      accessedFeatureFlags.add("enablePreciseSchedulingForPremountItemsOnAndroid")
+      enablePreciseSchedulingForPremountItemsOnAndroidCache = cached
+    }
+    return cached
+  }
+
   override fun enablePropsUpdateReconciliationAndroid(): Boolean {
     var cached = enablePropsUpdateReconciliationAndroidCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsProvider.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<79cd9812257f42d553b49a3f6d3d4989>>
+ * @generated SignedSource<<0f6129ccbcf7857785724f14b41edb2d>>
  */
 
 /**
@@ -63,6 +63,8 @@ public interface ReactNativeFeatureFlagsProvider {
 
   @DoNotStrip public fun enableMicrotasks(): Boolean
 
+  @DoNotStrip public fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean
+
   @DoNotStrip public fun enablePropsUpdateReconciliationAndroid(): Boolean
 
   @DoNotStrip public fun enableReportEventPaintTime(): Boolean

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.cpp

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<9e891a5d26221136d7334982fc2e99d3>>
+ * @generated SignedSource<<43b92dd984e985e09e3efad9c8fedf44>>
  */
 
 /**
@@ -159,6 +159,12 @@ class ReactNativeFeatureFlagsProviderHolder
     return method(javaProvider_);
   }
 
+  bool enablePreciseSchedulingForPremountItemsOnAndroid() override {
+    static const auto method =
+        getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("enablePreciseSchedulingForPremountItemsOnAndroid");
+    return method(javaProvider_);
+  }
+
   bool enablePropsUpdateReconciliationAndroid() override {
     static const auto method =
         getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("enablePropsUpdateReconciliationAndroid");
@@ -443,6 +449,11 @@ bool JReactNativeFeatureFlagsCxxInterop::enableMicrotasks(
   return ReactNativeFeatureFlags::enableMicrotasks();
 }
 
+bool JReactNativeFeatureFlagsCxxInterop::enablePreciseSchedulingForPremountItemsOnAndroid(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
+  return ReactNativeFeatureFlags::enablePreciseSchedulingForPremountItemsOnAndroid();
+}
+
 bool JReactNativeFeatureFlagsCxxInterop::enablePropsUpdateReconciliationAndroid(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
   return ReactNativeFeatureFlags::enablePropsUpdateReconciliationAndroid();
@@ -670,6 +681,9 @@ void JReactNativeFeatureFlagsCxxInterop::registerNatives() {
       makeNativeMethod(
         "enableMicrotasks",
         JReactNativeFeatureFlagsCxxInterop::enableMicrotasks),
+      makeNativeMethod(
+        "enablePreciseSchedulingForPremountItemsOnAndroid",
+        JReactNativeFeatureFlagsCxxInterop::enablePreciseSchedulingForPremountItemsOnAndroid),
       makeNativeMethod(
         "enablePropsUpdateReconciliationAndroid",
         JReactNativeFeatureFlagsCxxInterop::enablePropsUpdateReconciliationAndroid),

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.h

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<70edc4176da74aed5eaa1561a907a7ee>>
+ * @generated SignedSource<<54c94f9bfa07e41d978899dbce03469f>>
  */
 
 /**
@@ -90,6 +90,9 @@ class JReactNativeFeatureFlagsCxxInterop
   static bool enableMicrotasks(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 
+  static bool enablePreciseSchedulingForPremountItemsOnAndroid(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
+
   static bool enablePropsUpdateReconciliationAndroid(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.cpp

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<80b130f32b0bc59b9a9605777537feeb>>
+ * @generated SignedSource<<b04a641595d870bd9666281b3f0cfec5>>
  */
 
 /**
@@ -101,6 +101,10 @@ bool ReactNativeFeatureFlags::enableMicrotasks() {
   return getAccessor().enableMicrotasks();
 }
 
+bool ReactNativeFeatureFlags::enablePreciseSchedulingForPremountItemsOnAndroid() {
+  return getAccessor().enablePreciseSchedulingForPremountItemsOnAndroid();
+}
+
 bool ReactNativeFeatureFlags::enablePropsUpdateReconciliationAndroid() {
   return getAccessor().enablePropsUpdateReconciliationAndroid();
 }

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.h

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<3b5ff29faaf1575c051131bdf24a3237>>
+ * @generated SignedSource<<2cde82b474ab94cd05bdf5e04e700c13>>
  */
 
 /**
@@ -137,6 +137,11 @@ class ReactNativeFeatureFlags {
    */
   RN_EXPORT static bool enableMicrotasks();
 
+  /**
+   * Moves execution of pre-mount items to outside the choregrapher in the main thread, so we can estimate idle time more precisely (Android only).
+   */
+  RN_EXPORT static bool enablePreciseSchedulingForPremountItemsOnAndroid();
+
   /**
    * When enabled, Android will receive prop updates based on the differences between the last rendered shadow node and the last committed shadow node.
    */