Recycle CSSNodes

Summary: Adds a pool to recycle CSSNodes within UIManager. A follow-up diff will hook this up to a memory pressure listener to drop the pool on memory pressure.

Reviewed By: emilsjolander

Differential Revision: D4189532

fbshipit-source-id: 46583546f71a8c59853e1dd124de31657b3c617b

ReactAndroid/src/main/java/com/facebook/react/common/BUCK

@@ -7,14 +7,15 @@ SUB_PROJECTS = [
 android_library(
   name = 'common',
   srcs = glob(['**/*.java'], excludes=SUB_PROJECTS),
-  deps = [
-    ':build_config',
-    react_native_dep('third-party/java/infer-annotations:infer-annotations'),
-    react_native_dep('third-party/java/jsr-305:jsr-305'),
-  ],
   exported_deps = [
     react_native_dep('java/com/facebook/proguard/annotations:annotations'),
   ],
+  deps = [
+    ':build_config',
+    react_native_dep('third-party/android/support/v4:lib-support-v4'),
+    react_native_dep('third-party/java/infer-annotations:infer-annotations'),
+    react_native_dep('third-party/java/jsr-305:jsr-305'),
+  ],
   visibility = [
     'PUBLIC',
   ],

ReactAndroid/src/main/java/com/facebook/react/common/ClearableSynchronizedPool.java

@@ -0,0 +1,48 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react.common;
+
+import android.support.v4.util.Pools;
+
+/**
+ * Like {@link android.support.v4.util.Pools.SynchronizedPool} with the option to clear the pool
+ * (e.g. on memory pressure).
+ */
+public class ClearableSynchronizedPool<T> implements Pools.Pool<T> {
+
+  private final Object[] mPool;
+  private int mSize = 0;
+
+  public ClearableSynchronizedPool(int maxSize) {
+    mPool = new Object[maxSize];
+  }
+
+  @Override
+  public synchronized T acquire() {
+    if (mSize == 0) {
+      return null;
+    }
+    mSize--;
+    final int lastIndex = mSize;
+    T toReturn = (T) mPool[lastIndex];
+    mPool[lastIndex] = null;
+    return toReturn;
+  }
+
+  @Override
+  public synchronized boolean release(T obj) {
+    if (mSize == mPool.length) {
+      return false;
+    }
+    mPool[mSize] = obj;
+    mSize++;
+    return true;
+  }
+
+  public synchronized void clear() {
+    for (int i = 0; i < mSize; i++) {
+      mPool[i] = null;
+    }
+    mSize = 0;
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/uimanager/CSSNodePool.java

@@ -0,0 +1,28 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react.uimanager;
+
+import com.facebook.csslayout.CSSNode;
+import com.facebook.react.common.ClearableSynchronizedPool;
+
+/**
+ * Static holder for a recycling pool of CSSNodes.
+ */
+public class CSSNodePool {
+
+  private static final Object sInitLock = new Object();
+  private static ClearableSynchronizedPool<CSSNode> sPool;
+
+  public static ClearableSynchronizedPool<CSSNode> get() {
+    if (sPool != null) {
+      return sPool;
+    }
+
+    synchronized (sInitLock) {
+      if (sPool == null) {
+        sPool = new ClearableSynchronizedPool<CSSNode>(1024);
+      }
+      return sPool;
+    }
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/uimanager/ReactShadowNode.java

@@ -74,7 +74,15 @@ public class ReactShadowNode {
   private float mAbsoluteBottom;
   private final Spacing mDefaultPadding = new Spacing(0);
   private final Spacing mPadding = new Spacing(CSSConstants.UNDEFINED);
-  private final CSSNode mCSSNode = new CSSNode();
+  private final CSSNode mCSSNode;
+
+  public ReactShadowNode() {
+    CSSNode node = CSSNodePool.get().acquire();
+    if (node == null) {
+      node = new CSSNode();
+    }
+    mCSSNode = node;
+  }
 
   /**
    * Nodes that return {@code true} will be treated as "virtual" nodes. That is, nodes that are not
@@ -190,7 +198,7 @@ public class ReactShadowNode {
     return mChildren == null ? -1 : mChildren.indexOf(child);
   }
 
-  public void removeAllChildren() {
+  public void removeAndDisposeAllChildren() {
     if (getChildCount() == 0) {
       return;
     }
@@ -202,6 +210,8 @@ public class ReactShadowNode {
       }
       ReactShadowNode toRemove = getChildAt(i);
       toRemove.mParent = null;
+      toRemove.dispose();
+
       decrease += toRemove.mIsLayoutOnly ? toRemove.mTotalNativeChildren : 1;
     }
     Assertions.assertNotNull(mChildren).clear();
@@ -654,4 +664,9 @@ public class ReactShadowNode {
   public String toString() {
     return mCSSNode.toString();
   }
+
+  public void dispose() {
+    mCSSNode.reset();
+    CSSNodePool.get().release(mCSSNode);
+  }
 }

ReactAndroid/src/main/java/com/facebook/react/uimanager/UIImplementation.java

@@ -652,12 +652,17 @@ public class UIImplementation {
   }
 
   protected final void removeShadowNode(ReactShadowNode nodeToRemove) {
-    mNativeViewHierarchyOptimizer.handleRemoveNode(nodeToRemove);
+    removeShadowNodeRecursive(nodeToRemove);
+    nodeToRemove.dispose();
+  }
+
+  private void removeShadowNodeRecursive(ReactShadowNode nodeToRemove) {
+    NativeViewHierarchyOptimizer.handleRemoveNode(nodeToRemove);
     mShadowNodeRegistry.removeNode(nodeToRemove.getReactTag());
     for (int i = nodeToRemove.getChildCount() - 1; i >= 0; i--) {
-      removeShadowNode(nodeToRemove.getChildAt(i));
+      removeShadowNodeRecursive(nodeToRemove.getChildAt(i));
     }
-    nodeToRemove.removeAllChildren();
+    nodeToRemove.removeAndDisposeAllChildren();
   }
 
   private void measureLayout(int tag, int ancestorTag, int[] outputBuffer) {