165912365a
Motivation:
Avoid unnecessary iteration and `ArrayList` allocation.
Modification:
```
for (AbstractEpollChannel channel: channels.values()) {
array.add(channel);
}
```
replaced with
`array.addAll(channels.values())`
and
```
Collection<AbstractEpollChannel> array = new ArrayList<AbstractEpollChannel>(channels.size());
array.addAll(channels.values())
```
replaced with:
`AbstractEpollChannel[] localChannels = channels.values().toArray(new AbstractEpollChannel[0]);`
Result:
Simpler code in `EpollEventLoop.closeAll();`
483 lines
19 KiB
Java
483 lines
19 KiB
Java
/*
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* Copyright 2014 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.channel.epoll;
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import io.netty.channel.EventLoop;
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import io.netty.channel.EventLoopGroup;
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import io.netty.channel.SelectStrategy;
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import io.netty.channel.SingleThreadEventLoop;
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import io.netty.channel.epoll.AbstractEpollChannel.AbstractEpollUnsafe;
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import io.netty.channel.unix.FileDescriptor;
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import io.netty.channel.unix.IovArray;
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import io.netty.util.IntSupplier;
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import io.netty.util.collection.IntObjectHashMap;
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import io.netty.util.collection.IntObjectMap;
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import io.netty.util.concurrent.RejectedExecutionHandler;
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import io.netty.util.internal.ObjectUtil;
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import io.netty.util.internal.PlatformDependent;
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import io.netty.util.internal.logging.InternalLogger;
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import io.netty.util.internal.logging.InternalLoggerFactory;
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import java.io.IOException;
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import java.util.Queue;
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import java.util.concurrent.Executor;
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import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
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import static java.lang.Math.min;
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/**
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* {@link EventLoop} which uses epoll under the covers. Only works on Linux!
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*/
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class EpollEventLoop extends SingleThreadEventLoop {
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private static final InternalLogger logger = InternalLoggerFactory.getInstance(EpollEventLoop.class);
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private static final AtomicIntegerFieldUpdater<EpollEventLoop> WAKEN_UP_UPDATER =
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AtomicIntegerFieldUpdater.newUpdater(EpollEventLoop.class, "wakenUp");
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static {
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// Ensure JNI is initialized by the time this class is loaded by this time!
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// We use unix-common methods in this class which are backed by JNI methods.
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Epoll.ensureAvailability();
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}
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// Pick a number that no task could have previously used.
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private long prevDeadlineNanos = nanoTime() - 1;
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private final FileDescriptor epollFd;
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private final FileDescriptor eventFd;
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private final FileDescriptor timerFd;
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private final IntObjectMap<AbstractEpollChannel> channels = new IntObjectHashMap<AbstractEpollChannel>(4096);
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private final boolean allowGrowing;
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private final EpollEventArray events;
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// These are initialized on first use
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private IovArray iovArray;
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private NativeDatagramPacketArray datagramPacketArray;
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private final SelectStrategy selectStrategy;
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private final IntSupplier selectNowSupplier = new IntSupplier() {
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@Override
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public int get() throws Exception {
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return epollWaitNow();
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}
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};
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@SuppressWarnings("unused") // AtomicIntegerFieldUpdater
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private volatile int wakenUp;
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private volatile int ioRatio = 50;
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// See http://man7.org/linux/man-pages/man2/timerfd_create.2.html.
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private static final long MAX_SCHEDULED_TIMERFD_NS = 999999999;
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EpollEventLoop(EventLoopGroup parent, Executor executor, int maxEvents,
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SelectStrategy strategy, RejectedExecutionHandler rejectedExecutionHandler) {
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super(parent, executor, false, DEFAULT_MAX_PENDING_TASKS, rejectedExecutionHandler);
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selectStrategy = ObjectUtil.checkNotNull(strategy, "strategy");
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if (maxEvents == 0) {
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allowGrowing = true;
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events = new EpollEventArray(4096);
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} else {
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allowGrowing = false;
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events = new EpollEventArray(maxEvents);
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}
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boolean success = false;
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FileDescriptor epollFd = null;
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FileDescriptor eventFd = null;
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FileDescriptor timerFd = null;
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try {
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this.epollFd = epollFd = Native.newEpollCreate();
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this.eventFd = eventFd = Native.newEventFd();
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try {
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Native.epollCtlAdd(epollFd.intValue(), eventFd.intValue(), Native.EPOLLIN);
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} catch (IOException e) {
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throw new IllegalStateException("Unable to add eventFd filedescriptor to epoll", e);
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}
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this.timerFd = timerFd = Native.newTimerFd();
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try {
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Native.epollCtlAdd(epollFd.intValue(), timerFd.intValue(), Native.EPOLLIN | Native.EPOLLET);
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} catch (IOException e) {
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throw new IllegalStateException("Unable to add timerFd filedescriptor to epoll", e);
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}
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success = true;
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} finally {
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if (!success) {
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if (epollFd != null) {
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try {
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epollFd.close();
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} catch (Exception e) {
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// ignore
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}
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}
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if (eventFd != null) {
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try {
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eventFd.close();
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} catch (Exception e) {
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// ignore
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}
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}
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if (timerFd != null) {
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try {
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timerFd.close();
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} catch (Exception e) {
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// ignore
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}
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}
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}
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}
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}
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/**
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* Return a cleared {@link IovArray} that can be used for writes in this {@link EventLoop}.
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*/
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IovArray cleanIovArray() {
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if (iovArray == null) {
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iovArray = new IovArray();
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} else {
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iovArray.clear();
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}
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return iovArray;
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}
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/**
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* Return a cleared {@link NativeDatagramPacketArray} that can be used for writes in this {@link EventLoop}.
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*/
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NativeDatagramPacketArray cleanDatagramPacketArray() {
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if (datagramPacketArray == null) {
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datagramPacketArray = new NativeDatagramPacketArray();
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} else {
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datagramPacketArray.clear();
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}
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return datagramPacketArray;
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}
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@Override
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protected void wakeup(boolean inEventLoop) {
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if (!inEventLoop && WAKEN_UP_UPDATER.compareAndSet(this, 0, 1)) {
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// write to the evfd which will then wake-up epoll_wait(...)
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Native.eventFdWrite(eventFd.intValue(), 1L);
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}
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}
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/**
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* Register the given epoll with this {@link EventLoop}.
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*/
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void add(AbstractEpollChannel ch) throws IOException {
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assert inEventLoop();
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int fd = ch.socket.intValue();
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Native.epollCtlAdd(epollFd.intValue(), fd, ch.flags);
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channels.put(fd, ch);
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}
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/**
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* The flags of the given epoll was modified so update the registration
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*/
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void modify(AbstractEpollChannel ch) throws IOException {
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assert inEventLoop();
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Native.epollCtlMod(epollFd.intValue(), ch.socket.intValue(), ch.flags);
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}
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/**
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* Deregister the given epoll from this {@link EventLoop}.
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*/
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void remove(AbstractEpollChannel ch) throws IOException {
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assert inEventLoop();
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if (ch.isOpen()) {
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int fd = ch.socket.intValue();
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if (channels.remove(fd) != null) {
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// Remove the epoll. This is only needed if it's still open as otherwise it will be automatically
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// removed once the file-descriptor is closed.
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Native.epollCtlDel(epollFd.intValue(), ch.fd().intValue());
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}
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}
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}
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@Override
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protected Queue<Runnable> newTaskQueue(int maxPendingTasks) {
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// This event loop never calls takeTask()
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return maxPendingTasks == Integer.MAX_VALUE ? PlatformDependent.<Runnable>newMpscQueue()
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: PlatformDependent.<Runnable>newMpscQueue(maxPendingTasks);
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}
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/**
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* Returns the percentage of the desired amount of time spent for I/O in the event loop.
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*/
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public int getIoRatio() {
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return ioRatio;
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}
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/**
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* Sets the percentage of the desired amount of time spent for I/O in the event loop. The default value is
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* {@code 50}, which means the event loop will try to spend the same amount of time for I/O as for non-I/O tasks.
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*/
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public void setIoRatio(int ioRatio) {
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if (ioRatio <= 0 || ioRatio > 100) {
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throw new IllegalArgumentException("ioRatio: " + ioRatio + " (expected: 0 < ioRatio <= 100)");
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}
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this.ioRatio = ioRatio;
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}
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private int epollWait(boolean oldWakeup) throws IOException {
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// If a task was submitted when wakenUp value was 1, the task didn't get a chance to produce wakeup event.
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// So we need to check task queue again before calling epoll_wait. If we don't, the task might be pended
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// until epoll_wait was timed out. It might be pended until idle timeout if IdleStateHandler existed
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// in pipeline.
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if (oldWakeup && hasTasks()) {
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return epollWaitNow();
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}
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int delaySeconds;
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int delayNanos;
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long curDeadlineNanos = deadlineNanos();
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if (curDeadlineNanos == prevDeadlineNanos) {
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delaySeconds = -1;
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delayNanos = -1;
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} else {
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long totalDelay = delayNanos(System.nanoTime());
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prevDeadlineNanos = curDeadlineNanos;
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delaySeconds = (int) min(totalDelay / 1000000000L, Integer.MAX_VALUE);
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delayNanos = (int) min(totalDelay - delaySeconds * 1000000000L, MAX_SCHEDULED_TIMERFD_NS);
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}
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return Native.epollWait(epollFd, events, timerFd, delaySeconds, delayNanos);
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}
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private int epollWaitNow() throws IOException {
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return Native.epollWait(epollFd, events, timerFd, 0, 0);
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}
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private int epollBusyWait() throws IOException {
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return Native.epollBusyWait(epollFd, events);
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}
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@Override
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protected void run() {
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for (;;) {
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try {
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int strategy = selectStrategy.calculateStrategy(selectNowSupplier, hasTasks());
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switch (strategy) {
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case SelectStrategy.CONTINUE:
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continue;
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case SelectStrategy.BUSY_WAIT:
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strategy = epollBusyWait();
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break;
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case SelectStrategy.SELECT:
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strategy = epollWait(WAKEN_UP_UPDATER.getAndSet(this, 0) == 1);
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// 'wakenUp.compareAndSet(false, true)' is always evaluated
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// before calling 'selector.wakeup()' to reduce the wake-up
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// overhead. (Selector.wakeup() is an expensive operation.)
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//
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// However, there is a race condition in this approach.
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// The race condition is triggered when 'wakenUp' is set to
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// true too early.
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//
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// 'wakenUp' is set to true too early if:
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// 1) Selector is waken up between 'wakenUp.set(false)' and
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// 'selector.select(...)'. (BAD)
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// 2) Selector is waken up between 'selector.select(...)' and
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// 'if (wakenUp.get()) { ... }'. (OK)
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//
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// In the first case, 'wakenUp' is set to true and the
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// following 'selector.select(...)' will wake up immediately.
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// Until 'wakenUp' is set to false again in the next round,
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// 'wakenUp.compareAndSet(false, true)' will fail, and therefore
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// any attempt to wake up the Selector will fail, too, causing
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// the following 'selector.select(...)' call to block
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// unnecessarily.
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//
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// To fix this problem, we wake up the selector again if wakenUp
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// is true immediately after selector.select(...).
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// It is inefficient in that it wakes up the selector for both
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// the first case (BAD - wake-up required) and the second case
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// (OK - no wake-up required).
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if (wakenUp == 1) {
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Native.eventFdWrite(eventFd.intValue(), 1L);
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}
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// fallthrough
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default:
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}
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final int ioRatio = this.ioRatio;
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if (ioRatio == 100) {
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try {
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if (strategy > 0) {
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processReady(events, strategy);
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}
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} finally {
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// Ensure we always run tasks.
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runAllTasks();
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}
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} else {
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final long ioStartTime = System.nanoTime();
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try {
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if (strategy > 0) {
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processReady(events, strategy);
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}
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} finally {
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// Ensure we always run tasks.
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final long ioTime = System.nanoTime() - ioStartTime;
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runAllTasks(ioTime * (100 - ioRatio) / ioRatio);
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}
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}
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if (allowGrowing && strategy == events.length()) {
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//increase the size of the array as we needed the whole space for the events
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events.increase();
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}
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} catch (Throwable t) {
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handleLoopException(t);
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}
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// Always handle shutdown even if the loop processing threw an exception.
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try {
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if (isShuttingDown()) {
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closeAll();
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if (confirmShutdown()) {
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break;
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}
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}
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} catch (Throwable t) {
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handleLoopException(t);
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}
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}
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}
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/**
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* Visible only for testing!
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*/
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void handleLoopException(Throwable t) {
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logger.warn("Unexpected exception in the selector loop.", t);
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// Prevent possible consecutive immediate failures that lead to
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// excessive CPU consumption.
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try {
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Thread.sleep(1000);
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} catch (InterruptedException e) {
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// Ignore.
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}
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}
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private void closeAll() {
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try {
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epollWaitNow();
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} catch (IOException ignore) {
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// ignore on close
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}
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// Using the intermediate collection to prevent ConcurrentModificationException.
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// In the `close()` method, the channel is deleted from `channels` map.
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AbstractEpollChannel[] localChannels = channels.values().toArray(new AbstractEpollChannel[0]);
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for (AbstractEpollChannel ch : localChannels) {
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ch.unsafe().close(ch.unsafe().voidPromise());
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}
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}
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private void processReady(EpollEventArray events, int ready) {
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for (int i = 0; i < ready; i ++) {
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final int fd = events.fd(i);
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if (fd == eventFd.intValue()) {
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// consume wakeup event.
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Native.eventFdRead(fd);
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} else if (fd == timerFd.intValue()) {
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// consume wakeup event, necessary because the timer is added with ET mode.
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Native.timerFdRead(fd);
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} else {
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final long ev = events.events(i);
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AbstractEpollChannel ch = channels.get(fd);
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if (ch != null) {
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// Don't change the ordering of processing EPOLLOUT | EPOLLRDHUP / EPOLLIN if you're not 100%
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// sure about it!
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// Re-ordering can easily introduce bugs and bad side-effects, as we found out painfully in the
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// past.
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AbstractEpollUnsafe unsafe = (AbstractEpollUnsafe) ch.unsafe();
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// First check for EPOLLOUT as we may need to fail the connect ChannelPromise before try
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// to read from the file descriptor.
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// See https://github.com/netty/netty/issues/3785
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//
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// It is possible for an EPOLLOUT or EPOLLERR to be generated when a connection is refused.
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// In either case epollOutReady() will do the correct thing (finish connecting, or fail
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// the connection).
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// See https://github.com/netty/netty/issues/3848
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if ((ev & (Native.EPOLLERR | Native.EPOLLOUT)) != 0) {
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// Force flush of data as the epoll is writable again
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unsafe.epollOutReady();
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}
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// Check EPOLLIN before EPOLLRDHUP to ensure all data is read before shutting down the input.
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// See https://github.com/netty/netty/issues/4317.
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//
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// If EPOLLIN or EPOLLERR was received and the channel is still open call epollInReady(). This will
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// try to read from the underlying file descriptor and so notify the user about the error.
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if ((ev & (Native.EPOLLERR | Native.EPOLLIN)) != 0) {
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// The Channel is still open and there is something to read. Do it now.
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unsafe.epollInReady();
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}
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// Check if EPOLLRDHUP was set, this will notify us for connection-reset in which case
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// we may close the channel directly or try to read more data depending on the state of the
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// Channel and als depending on the AbstractEpollChannel subtype.
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if ((ev & Native.EPOLLRDHUP) != 0) {
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unsafe.epollRdHupReady();
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}
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} else {
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// We received an event for an fd which we not use anymore. Remove it from the epoll_event set.
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try {
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Native.epollCtlDel(epollFd.intValue(), fd);
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} catch (IOException ignore) {
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// This can happen but is nothing we need to worry about as we only try to delete
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// the fd from the epoll set as we not found it in our mappings. So this call to
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// epollCtlDel(...) is just to ensure we cleanup stuff and so may fail if it was
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// deleted before or the file descriptor was closed before.
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}
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}
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}
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}
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}
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@Override
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protected void cleanup() {
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try {
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try {
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epollFd.close();
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} catch (IOException e) {
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logger.warn("Failed to close the epoll fd.", e);
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}
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try {
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eventFd.close();
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} catch (IOException e) {
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logger.warn("Failed to close the event fd.", e);
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}
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try {
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timerFd.close();
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} catch (IOException e) {
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logger.warn("Failed to close the timer fd.", e);
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}
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} finally {
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// release native memory
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if (iovArray != null) {
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iovArray.release();
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iovArray = null;
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}
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if (datagramPacketArray != null) {
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datagramPacketArray.release();
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datagramPacketArray = null;
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}
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events.free();
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}
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}
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}
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