Replace EventDispatcherImpl with LockFreeEventDispatcherImpl
Summary: EventDispatcherImpl uses synchronized blocks all over to make it thread-safe. I'm concerned about the perf implications of this and creating contention between JS and UI threads. This is locked behind a feature flag. Enabled only for Fabric in StaticViewConfig mode, and a feature flag, for now. Changelog: [Internal] Reviewed By: mdvacca Differential Revision: D28591331 fbshipit-source-id: ea8f93a2e1343ce37fa78690dcb62fe03594120f
This commit is contained in:
Joshua Gross
Facebook GitHub Bot
Родитель
a2ab3fccd0
Коммит
0510821170
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@ -97,6 +97,8 @@ public class ReactFeatureFlags {
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/** Enables Fabric for LogBox */
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public static boolean enableFabricInLogBox = false;
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public static boolean enableLockFreeEventDispatcher = false;
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//
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// ScrollView C++ UpdateState vs onScroll race fixes
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//
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@ -78,6 +78,7 @@ import com.facebook.react.uimanager.ViewManagerPropertyUpdater;
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import com.facebook.react.uimanager.ViewManagerRegistry;
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import com.facebook.react.uimanager.events.EventDispatcher;
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import com.facebook.react.uimanager.events.EventDispatcherImpl;
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import com.facebook.react.uimanager.events.LockFreeEventDispatcherImpl;
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import com.facebook.react.views.text.TextLayoutManager;
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import com.facebook.react.views.text.TextLayoutManagerMapBuffer;
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import java.util.HashMap;
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@ -171,7 +172,10 @@ public class FabricUIManager implements UIManager, LifecycleEventListener {
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mMountingManager = new MountingManager(viewManagerRegistry);
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mMountItemDispatcher =
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new MountItemDispatcher(mMountingManager, new MountItemDispatchListener());
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mEventDispatcher = new EventDispatcherImpl(reactContext);
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mEventDispatcher =
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ReactFeatureFlags.enableLockFreeEventDispatcher
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? new LockFreeEventDispatcherImpl(reactContext)
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: new EventDispatcherImpl(reactContext);
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mShouldDeallocateEventDispatcher = true;
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mEventBeatManager = eventBeatManager;
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mReactApplicationContext.addLifecycleEventListener(this);
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@ -0,0 +1,374 @@
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/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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package com.facebook.react.uimanager.events;
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import com.facebook.infer.annotation.Assertions;
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import com.facebook.react.bridge.LifecycleEventListener;
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import com.facebook.react.bridge.ReactApplicationContext;
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import com.facebook.react.bridge.UiThreadUtil;
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import com.facebook.react.common.MapBuilder;
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import com.facebook.react.common.build.ReactBuildConfig;
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import com.facebook.react.modules.core.ChoreographerCompat;
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import com.facebook.react.modules.core.ReactChoreographer;
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import com.facebook.react.uimanager.common.UIManagerType;
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import com.facebook.systrace.Systrace;
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import java.util.ArrayList;
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import java.util.Comparator;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.concurrent.ConcurrentLinkedQueue;
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import java.util.concurrent.CopyOnWriteArrayList;
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import java.util.concurrent.atomic.AtomicInteger;
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/**
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* Class responsible for dispatching UI events to JS. The main purpose of this class is to act as an
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* intermediary between UI code generating events and JS, making sure we don't send more events than
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* JS can process.
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*
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* <p>To use it, create a subclass of {@link Event} and call {@link #dispatchEvent(Event)} whenever
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* there's a UI event to dispatch.
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*
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* <p>This class works by installing a Choreographer frame callback on the main thread. This
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* callback then enqueues a runnable on the JS thread (if one is not already pending) that is
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* responsible for actually dispatch events to JS. This implementation depends on the properties
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* that 1) FrameCallbacks run after UI events have been processed in Choreographer.java 2) when we
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* enqueue a runnable on the JS queue thread, it won't be called until after any previously enqueued
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* JS jobs have finished processing
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*
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* <p>If JS is taking a long time processing events, then the UI events generated on the UI thread
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* can be coalesced into fewer events so that when the runnable runs, we don't overload JS with a
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* ton of events and make it get even farther behind.
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*
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* <p>Ideally, we don't need this and JS is fast enough to process all the events each frame, but
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* bad things happen, including load on CPUs from the system, and we should handle this case well.
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*
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* <p>== Event Cookies ==
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*
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* <p>An event cookie is made up of the event type id, view tag, and a custom coalescing key. Only
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* Events that have the same cookie can be coalesced.
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*
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* <p>Event Cookie Composition: VIEW_TAG_MASK = 0x00000000ffffffff EVENT_TYPE_ID_MASK =
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* 0x0000ffff00000000 COALESCING_KEY_MASK = 0xffff000000000000
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*
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* <p>This is a copy of EventDispatcherImpl, meant only to remove locking and synchronization.
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*/
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public class LockFreeEventDispatcherImpl implements EventDispatcher, LifecycleEventListener {
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private static final Comparator<Event> EVENT_COMPARATOR =
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new Comparator<Event>() {
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@Override
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public int compare(Event lhs, Event rhs) {
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if (lhs == null && rhs == null) {
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return 0;
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}
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if (lhs == null) {
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return -1;
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}
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if (rhs == null) {
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return 1;
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}
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long diff = lhs.getTimestampMs() - rhs.getTimestampMs();
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if (diff == 0) {
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return 0;
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} else if (diff < 0) {
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return -1;
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} else {
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return 1;
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}
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}
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};
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private final ReactApplicationContext mReactContext;
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private final Map<String, Short> mEventNameToEventId = MapBuilder.newHashMap();
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private final LockFreeEventDispatcherImpl.DispatchEventsRunnable mDispatchEventsRunnable =
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new LockFreeEventDispatcherImpl.DispatchEventsRunnable();
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private final ConcurrentLinkedQueue<Event> mEventStaging = new ConcurrentLinkedQueue<>();
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private final CopyOnWriteArrayList<EventDispatcherListener> mListeners =
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new CopyOnWriteArrayList<>();
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private final CopyOnWriteArrayList<BatchEventDispatchedListener> mPostEventDispatchListeners =
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new CopyOnWriteArrayList<>();
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private final LockFreeEventDispatcherImpl.ScheduleDispatchFrameCallback mCurrentFrameCallback =
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new LockFreeEventDispatcherImpl.ScheduleDispatchFrameCallback();
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private final AtomicInteger mHasDispatchScheduledCount = new AtomicInteger();
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private volatile ReactEventEmitter mReactEventEmitter;
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private short mNextEventTypeId = 0;
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private volatile boolean mHasDispatchScheduled = false;
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public LockFreeEventDispatcherImpl(ReactApplicationContext reactContext) {
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mReactContext = reactContext;
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mReactContext.addLifecycleEventListener(this);
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mReactEventEmitter = new ReactEventEmitter(mReactContext);
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}
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/** Sends the given Event to JS, coalescing eligible events if JS is backed up. */
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public void dispatchEvent(Event event) {
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Assertions.assertCondition(event.isInitialized(), "Dispatched event hasn't been initialized");
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for (EventDispatcherListener listener : mListeners) {
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listener.onEventDispatch(event);
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}
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mEventStaging.add(event);
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Systrace.startAsyncFlow(
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Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, event.getEventName(), event.getUniqueID());
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maybePostFrameCallbackFromNonUI();
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}
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public void dispatchAllEvents() {
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maybePostFrameCallbackFromNonUI();
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}
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private void maybePostFrameCallbackFromNonUI() {
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if (mReactEventEmitter != null) {
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// If the host activity is paused, the frame callback may not be currently
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// posted. Ensure that it is so that this event gets delivered promptly.
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mCurrentFrameCallback.maybePostFromNonUI();
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} else {
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// No JS application has started yet, or resumed. This can happen when a ReactRootView is
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// added to view hierarchy, but ReactContext creation has not completed yet. In this case, any
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// touch event dispatch will hit this codepath, and we simply queue them so that they
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// are dispatched once ReactContext creation completes and JS app is running.
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}
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}
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/** Add a listener to this EventDispatcher. */
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public void addListener(EventDispatcherListener listener) {
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mListeners.add(listener);
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}
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/** Remove a listener from this EventDispatcher. */
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public void removeListener(EventDispatcherListener listener) {
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mListeners.remove(listener);
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}
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public void addBatchEventDispatchedListener(BatchEventDispatchedListener listener) {
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mPostEventDispatchListeners.add(listener);
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}
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public void removeBatchEventDispatchedListener(BatchEventDispatchedListener listener) {
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mPostEventDispatchListeners.remove(listener);
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}
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@Override
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public void onHostResume() {
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maybePostFrameCallbackFromNonUI();
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}
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@Override
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public void onHostPause() {
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stopFrameCallback();
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}
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@Override
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public void onHostDestroy() {
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stopFrameCallback();
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}
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public void onCatalystInstanceDestroyed() {
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UiThreadUtil.runOnUiThread(
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new Runnable() {
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@Override
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public void run() {
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stopFrameCallback();
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}
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});
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}
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private void stopFrameCallback() {
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UiThreadUtil.assertOnUiThread();
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mCurrentFrameCallback.stop();
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}
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/**
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* We use a staging data structure so that all UI events generated in a single frame are
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* dispatched at once. Otherwise, a JS runnable enqueued in a previous frame could run while the
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* UI thread is in the process of adding UI events and we might incorrectly send one event this
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* frame and another from this frame during the next.
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*/
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private ArrayList<Event> moveStagedEventsToDispatchQueue() {
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ArrayList<Event> eventsToDispatchTmp = new ArrayList<>(16);
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Map<Long, Event> eventCookieToEventMap = new HashMap<>();
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while (true) {
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Event event = mEventStaging.poll();
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if (event == null) {
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break;
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}
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if (!event.canCoalesce()) {
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eventsToDispatchTmp.add(event);
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continue;
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}
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long eventCookie =
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getEventCookie(event.getViewTag(), event.getEventName(), event.getCoalescingKey());
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Event eventToAdd = null;
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Event eventToDispose = null;
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if (!eventCookieToEventMap.containsKey(eventCookie)) {
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eventToAdd = event;
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eventCookieToEventMap.put(eventCookie, event);
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} else {
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Event lastEvent = eventCookieToEventMap.get(eventCookie);
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Event coalescedEvent = event.coalesce(lastEvent);
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if (coalescedEvent != lastEvent) {
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eventToAdd = coalescedEvent;
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eventCookieToEventMap.put(eventCookie, eventToAdd);
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eventToDispose = lastEvent;
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} else {
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eventToDispose = event;
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}
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}
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if (eventToAdd != null) {
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eventsToDispatchTmp.add(eventToAdd);
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}
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if (eventToDispose != null) {
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eventToDispose.dispose();
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eventsToDispatchTmp.remove(eventToDispose);
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}
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}
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return eventsToDispatchTmp;
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}
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private long getEventCookie(int viewTag, String eventName, short coalescingKey) {
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short eventTypeId;
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Short eventIdObj = mEventNameToEventId.get(eventName);
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if (eventIdObj != null) {
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eventTypeId = eventIdObj;
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} else {
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eventTypeId = mNextEventTypeId++;
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mEventNameToEventId.put(eventName, eventTypeId);
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}
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return getEventCookie(viewTag, eventTypeId, coalescingKey);
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}
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private static long getEventCookie(int viewTag, short eventTypeId, short coalescingKey) {
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return viewTag
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| (((long) eventTypeId) & 0xffff) << 32
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| (((long) coalescingKey) & 0xffff) << 48;
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}
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public void registerEventEmitter(@UIManagerType int uiManagerType, RCTEventEmitter eventEmitter) {
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mReactEventEmitter.register(uiManagerType, eventEmitter);
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}
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public void registerEventEmitter(
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@UIManagerType int uiManagerType, RCTModernEventEmitter eventEmitter) {
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mReactEventEmitter.register(uiManagerType, eventEmitter);
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}
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public void unregisterEventEmitter(@UIManagerType int uiManagerType) {
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mReactEventEmitter.unregister(uiManagerType);
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}
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private class ScheduleDispatchFrameCallback extends ChoreographerCompat.FrameCallback {
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private volatile boolean mIsPosted = false;
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private boolean mShouldStop = false;
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@Override
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public void doFrame(long frameTimeNanos) {
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UiThreadUtil.assertOnUiThread();
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if (mShouldStop) {
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mIsPosted = false;
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} else {
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post();
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}
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Systrace.beginSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, "ScheduleDispatchFrameCallback");
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try {
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if (!mHasDispatchScheduled) {
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mHasDispatchScheduled = true;
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Systrace.startAsyncFlow(
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Systrace.TRACE_TAG_REACT_JAVA_BRIDGE,
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"ScheduleDispatchFrameCallback",
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mHasDispatchScheduledCount.get());
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mReactContext.runOnJSQueueThread(mDispatchEventsRunnable);
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}
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} finally {
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Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
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}
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}
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public void stop() {
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mShouldStop = true;
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}
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public void maybePost() {
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if (!mIsPosted) {
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mIsPosted = true;
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post();
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}
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}
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private void post() {
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ReactChoreographer.getInstance()
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.postFrameCallback(ReactChoreographer.CallbackType.TIMERS_EVENTS, mCurrentFrameCallback);
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}
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public void maybePostFromNonUI() {
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if (mIsPosted) {
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return;
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}
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// We should only hit this slow path when we receive events while the host activity is paused.
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if (mReactContext.isOnUiQueueThread()) {
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maybePost();
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} else {
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mReactContext.runOnUiQueueThread(
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new Runnable() {
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@Override
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public void run() {
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maybePost();
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}
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});
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}
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}
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}
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private class DispatchEventsRunnable implements Runnable {
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@Override
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public void run() {
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Systrace.beginSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, "DispatchEventsRunnable");
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try {
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Systrace.endAsyncFlow(
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Systrace.TRACE_TAG_REACT_JAVA_BRIDGE,
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"ScheduleDispatchFrameCallback",
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mHasDispatchScheduledCount.getAndIncrement());
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mHasDispatchScheduled = false;
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Assertions.assertNotNull(mReactEventEmitter);
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ArrayList<Event> eventsToDispatch = moveStagedEventsToDispatchQueue();
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for (Event event : eventsToDispatch) {
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if (ReactBuildConfig.DEBUG) {
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Assertions.assertNotNull(event);
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}
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Systrace.endAsyncFlow(
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Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, event.getEventName(), event.getUniqueID());
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event.dispatchModern(mReactEventEmitter);
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event.dispose();
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}
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for (BatchEventDispatchedListener listener : mPostEventDispatchListeners) {
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listener.onBatchEventDispatched();
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}
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} finally {
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Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
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}
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}
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}
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}
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