Faster event processing when epoll transport is used

Motivation:

Before we used a long[] to store the ready events, this had a few problems and limitations:
 - An extra loop was needed to translate between epoll_event and our long
 - JNI may need to do extra memory copy if the JVM not supports pinning
 - More branches

Modifications:

- Introduce a EpollEventArray which allows to directly write in a struct epoll_event* and pass it to epoll_wait.

Result:

Better speed when using native transport, as shown in the benchmark.

Before:
[xxx@xxx wrk]$ ./wrk -H 'Connection: keep-alive' -d 120 -c 256 -t 16 -s scripts/pipeline-many.lua  http://xxx:8080/plaintext
Running 2m test @ http://xxx:8080/plaintext
 16 threads and 256 connections
 Thread Stats   Avg      Stdev     Max   +/- Stdev
   Latency    14.56ms    8.64ms 117.15ms   80.58%
   Req/Sec   286.17k    38.71k  421.48k    68.17%
 546324329 requests in 2.00m, 73.78GB read
Requests/sec: 4553438.39
Transfer/sec:    629.66MB

After:
[xxx@xxx wrk]$ ./wrk -H 'Connection: keep-alive' -d 120 -c 256 -t 16 -s scripts/pipeline-many.lua  http://xxx:8080/plaintext
Running 2m test @ http://xxx:8080/plaintext
 16 threads and 256 connections
 Thread Stats   Avg      Stdev     Max   +/- Stdev
   Latency    14.12ms    8.69ms 100.40ms   83.08%
   Req/Sec   294.79k    40.23k  472.70k    66.75%
 555997226 requests in 2.00m, 75.08GB read
Requests/sec: 4634343.40
Transfer/sec:    640.85MB

transport-native-epoll/src/main/c/io_netty_channel_epoll_Native.c

@@ -30,6 +30,7 @@
 #include <arpa/inet.h>
 #include <fcntl.h>
 #include <sys/utsname.h>
+#include <stddef.h>
 #include "io_netty_channel_epoll_Native.h"
 
 // optional
@@ -104,20 +105,12 @@ char* exceptionMessage(char* msg, int error) {
     return result;
 }
 
-jint epollCtl(JNIEnv* env, jint efd, int op, jint fd, jint flags, jint id) {
+jint epollCtl(JNIEnv* env, jint efd, int op, jint fd, jint flags) {
-    uint32_t events = (flags & EPOLL_EDGE) ? EPOLLET : 0;
+    uint32_t events = flags;
-
-    if (flags & EPOLL_READ) {
-        events |= EPOLLIN | EPOLLRDHUP;
-    }
-    if (flags & EPOLL_WRITE) {
-        events |= EPOLLOUT;
-    }
 
     struct epoll_event ev = {
-        .events = events,
+        .data.fd = fd,
-        // encode the id into the events
+        .events = events
-        .data.u64 = (((uint64_t) id) << 32L)
     };
 
     return epoll_ctl(efd, op, fd, &ev);
@@ -620,9 +613,8 @@ JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollCreate(JNIEnv* en
     return efd;
 }
 
-JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollWait(JNIEnv* env, jclass clazz, jint efd, jlongArray events, jint timeout) {
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollWait0(JNIEnv* env, jclass clazz, jint efd, jlong address, jint len, jint timeout) {
-    int len = (*env)->GetArrayLength(env, events);
+    struct epoll_event *ev = (struct epoll_event*) address;
-    struct epoll_event ev[len];
     int ready;
     int err;
     do {
@@ -631,60 +623,20 @@ JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollWait(JNIEnv* env,
     } while (ready == -1 && ((err = errno) == EINTR));
 
     if (ready < 0) {
-         throwIOException(env, exceptionMessage("epoll_wait() failed: ", err));
+         return -err;
-         return -1;
     }
-    if (ready == 0) {
-        // nothing ready for process
-        return 0;
-    }
-
-    jboolean isCopy;
-    // Use GetPrimitiveArrayCritical and ReleasePrimitiveArrayCritical to signal the VM that we really would like
-    // to not do a memory copy here. This is ok as we not do any blocking action here anyway.
-    // This is important as the VM may suspend GC for the time!
-    jlong* elements = (*env)->GetPrimitiveArrayCritical(env, events, &isCopy);
-    if (elements == NULL) {
-        // No memory left ?!?!?
-        throwOutOfMemoryError(env);
-        return -1;
-    }
-    int i;
-    for (i = 0; i < ready; i++) {
-        // store the ready ops and id
-        elements[i] = (jlong) ev[i].data.u64;
-        if (ev[i].events & EPOLLIN) {
-            elements[i] |= EPOLL_READ;
-        }
-        if (ev[i].events & EPOLLRDHUP) {
-            elements[i] |= EPOLL_RDHUP;
-        }
-        if (ev[i].events & EPOLLOUT) {
-            elements[i] |= EPOLL_WRITE;
-        }
-    }
-    jint mode;
-    // release again to prevent memory leak
-    if (isCopy) {
-        mode = 0;
-    } else {
-        // was just pinned so use JNI_ABORT to eliminate not needed copy.
-        mode = JNI_ABORT;
-    }
-    (*env)->ReleasePrimitiveArrayCritical(env, events, elements, mode);
-
     return ready;
 }
 
-JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_epollCtlAdd(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags, jint id) {
+JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_epollCtlAdd(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags) {
-    if (epollCtl(env, efd, EPOLL_CTL_ADD, fd, flags, id) < 0) {
+    if (epollCtl(env, efd, EPOLL_CTL_ADD, fd, flags) < 0) {
         int err = errno;
         throwRuntimeException(env, exceptionMessage("epoll_ctl() failed: ", err));
     }
 }
 
-JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_epollCtlMod(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags, jint id) {
+JNIEXPORT void JNICALL Java_io_netty_channel_epoll_Native_epollCtlMod(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags) {
-    if (epollCtl(env, efd, EPOLL_CTL_MOD, fd, flags, id) < 0) {
+    if (epollCtl(env, efd, EPOLL_CTL_MOD, fd, flags) < 0) {
         int err = errno;
         throwRuntimeException(env, exceptionMessage("epoll_ctl() failed: ", err));
     }
@@ -1526,4 +1478,26 @@ JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_sendFd0(JNIEnv* env, j
     return -1;
 }
 
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollet(JNIEnv* env, jclass clazz) {
+    return EPOLLET;
+}
 
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollin(JNIEnv* env, jclass clazz) {
+    return EPOLLIN;
+}
+
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollout(JNIEnv* env, jclass clazz) {
+    return EPOLLOUT;
+}
+
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_epollrdhup(JNIEnv* env, jclass clazz) {
+    return EPOLLRDHUP;
+}
+
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_sizeofEpollEvent(JNIEnv* env, jclass clazz) {
+    return sizeof(struct epoll_event);
+}
+
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_offsetofEpollData(JNIEnv* env, jclass clazz) {
+    return offsetof(struct epoll_event, data);
+}

transport-native-epoll/src/main/c/io_netty_channel_epoll_Native.h

@@ -16,12 +16,6 @@
 #include <jni.h>
 #include <limits.h>
 
-#define EPOLL_READ 0x01
-#define EPOLL_WRITE 0x02
-#define EPOLL_RDHUP 0x04
-#define EPOLL_EDGE 0x08
-
-
 // Define SO_REUSEPORT if not found to fix build issues.
 // See https://github.com/netty/netty/issues/2558
 #ifndef SO_REUSEPORT
@@ -43,9 +37,9 @@ jint Java_io_netty_channel_epoll_Native_eventFd(JNIEnv* env, jclass clazz);
 void Java_io_netty_channel_epoll_Native_eventFdWrite(JNIEnv* env, jclass clazz, jint fd, jlong value);
 void Java_io_netty_channel_epoll_Native_eventFdRead(JNIEnv* env, jclass clazz, jint fd);
 jint Java_io_netty_channel_epoll_Native_epollCreate(JNIEnv* env, jclass clazz);
-jint Java_io_netty_channel_epoll_Native_epollWait(JNIEnv* env, jclass clazz, jint efd, jlongArray events, jint timeout);
+jint Java_io_netty_channel_epoll_Native_epollWait0(JNIEnv* env, jclass clazz, jint efd, jlong address, jint length, jint timeout);
-void Java_io_netty_channel_epoll_Native_epollCtlAdd(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags, jint id);
+void Java_io_netty_channel_epoll_Native_epollCtlAdd(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags);
-void Java_io_netty_channel_epoll_Native_epollCtlMod(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags, jint id);
+void Java_io_netty_channel_epoll_Native_epollCtlMod(JNIEnv* env, jclass clazz, jint efd, jint fd, jint flags);
 void  Java_io_netty_channel_epoll_Native_epollCtlDel(JNIEnv* env, jclass clazz, jint efd, jint fd);
 jint Java_io_netty_channel_epoll_Native_write0(JNIEnv* env, jclass clazz, jint fd, jobject jbuffer, jint pos, jint limit);
 jint Java_io_netty_channel_epoll_Native_writeAddress0(JNIEnv* env, jclass clazz, jint fd, jlong address, jint pos, jint limit);
@@ -117,3 +111,10 @@ jint Java_io_netty_channel_epoll_Native_errnoEAGAIN(JNIEnv* env, jclass clazz);
 jint Java_io_netty_channel_epoll_Native_errnoEWOULDBLOCK(JNIEnv* env, jclass clazz);
 jint Java_io_netty_channel_epoll_Native_errnoEINPROGRESS(JNIEnv* env, jclass clazz);
 jstring Java_io_netty_channel_epoll_Native_strError(JNIEnv* env, jclass clazz, jint err);
+
+jint Java_io_netty_channel_epoll_Native_epollin(JNIEnv* env, jclass clazz);
+jint Java_io_netty_channel_epoll_Native_epollout(JNIEnv* env, jclass clazz);
+jint Java_io_netty_channel_epoll_Native_epollrdhup(JNIEnv* env, jclass clazz);
+jint Java_io_netty_channel_epoll_Native_epollet(JNIEnv* env, jclass clazz);
+jint Java_io_netty_channel_epoll_Native_sizeofEpollEvent(JNIEnv* env, jclass clazz);
+jint Java_io_netty_channel_epoll_Native_offsetofEpollData(JNIEnv* env, jclass clazz);

transport-native-epoll/src/main/java/io/netty/channel/epoll/AbstractEpollChannel.java

@@ -38,7 +38,6 @@ abstract class AbstractEpollChannel extends AbstractChannel {
     protected int flags = Native.EPOLLET;
 
     protected volatile boolean active;
-    int id;
 
     AbstractEpollChannel(int fd, int flag) {
         this(null, fd, flag, false);

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollEventArray.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2015 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.channel.epoll;
+
+import io.netty.util.internal.PlatformDependent;
+
+/**
+ * This is an internal datastructure which can be directly passed to epoll_wait to reduce the overhead.
+ *
+ * typedef union epoll_data {
+ *     void        *ptr;
+ *     int          fd;
+ *     uint32_t     u32;
+ *     uint64_t     u64;
+ * } epoll_data_t;
+ *
+ * struct epoll_event {
+ *     uint32_t     events;      // Epoll events
+ *     epoll_data_t data;        // User data variable
+ * };
+ *
+ * We use {@code fd} if the {@code epoll_data union} to store the actual file descriptor of an
+ * {@link AbstractEpollChannel} and so be able to map it later.
+ */
+final class EpollEventArray {
+    // Size of the epoll_event struct
+    private static final int EPOLL_EVENT_SIZE = Native.sizeofEpollEvent();
+    // The offsiet of the data union in the epoll_event struct
+    private static final int EPOLL_DATA_OFFSET = Native.offsetofEpollData();
+
+    private long memoryAddress;
+    private int length;
+
+    EpollEventArray(int length) {
+        if (length < 1) {
+            throw new IllegalArgumentException("length must be >= 1 but was " + length);
+        }
+        this.length = length;
+        memoryAddress = allocate(length);
+    }
+
+    private static long allocate(int length) {
+        return PlatformDependent.allocateMemory(length * EPOLL_EVENT_SIZE);
+    }
+
+    /**
+     * Return the {@code memoryAddress} which points to the start of this {@link EpollEventArray}.
+     */
+    long memoryAddress() {
+        return memoryAddress;
+    }
+
+    /**
+     * Return the length of the {@link EpollEventArray} which represent the maximum number of {@code epoll_events}
+     * that can be stored in it.
+     */
+    int length() {
+        return length;
+    }
+
+    /**
+     * Increase the storage of this {@link EpollEventArray}.
+     */
+    void increase() {
+        // double the size
+        length <<= 1;
+        free();
+        memoryAddress = allocate(length);
+    }
+
+    /**
+     * Free this {@link EpollEventArray}. Any usage after calling this method may segfault the JVM!
+     */
+    void free() {
+        PlatformDependent.freeMemory(memoryAddress);
+    }
+
+    /**
+     * Return the events for the {@code epoll_event} on this index.
+     */
+    int events(int index) {
+        return PlatformDependent.getInt(memoryAddress + index * EPOLL_EVENT_SIZE);
+    }
+
+    /**
+     * Return the file descriptor for the {@code epoll_event} on this index.
+     */
+    int fd(int index) {
+        return PlatformDependent.getInt(memoryAddress + index * EPOLL_EVENT_SIZE + EPOLL_DATA_OFFSET);
+    }
+}

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollEventLoop.java

@@ -50,11 +50,9 @@ final class EpollEventLoop extends SingleThreadEventLoop {
 
     private final int epollFd;
     private final int eventFd;
-    private final IntObjectMap<AbstractEpollChannel> ids = new IntObjectHashMap<AbstractEpollChannel>();
+    private final IntObjectMap<AbstractEpollChannel> channels = new IntObjectHashMap<AbstractEpollChannel>(4096);
     private final boolean allowGrowing;
-    private long[] events;
+    private final EpollEventArray events;
-
-    private int id;
 
     @SuppressWarnings("unused")
     private volatile int wakenUp;
@@ -64,10 +62,10 @@ final class EpollEventLoop extends SingleThreadEventLoop {
         super(parent, executor, false);
         if (maxEvents == 0) {
             allowGrowing = true;
-            events = new long[128];
+            events = new EpollEventArray(4096);
         } else {
             allowGrowing = false;
-            events = new long[maxEvents];
+            events = new EpollEventArray(maxEvents);
         }
         boolean success = false;
         int epollFd = -1;
@@ -75,7 +73,7 @@ final class EpollEventLoop extends SingleThreadEventLoop {
         try {
             this.epollFd = epollFd = Native.epollCreate();
             this.eventFd = eventFd = Native.eventFd();
-            Native.epollCtlAdd(epollFd, eventFd, Native.EPOLLIN, 0);
+            Native.epollCtlAdd(epollFd, eventFd, Native.EPOLLIN);
             success = true;
         } finally {
             if (!success) {
@@ -97,29 +95,6 @@ final class EpollEventLoop extends SingleThreadEventLoop {
         }
     }
 
-    private int nextId() {
-        int id = this.id;
-        if (id == Integer.MAX_VALUE) {
-            // We used all possible ints in the past ( 1 - Integer.MAX_VALUE), time to scrub the stored channels
-            // and re-assign ids.
-            AbstractEpollChannel[] channels = ids.values(AbstractEpollChannel.class);
-            ids.clear();
-
-            id = 0;
-
-            for (AbstractEpollChannel ch: channels) {
-                id++;
-                ch.id = id;
-                ids.put(ch.id, ch);
-            }
-            if (id == Integer.MAX_VALUE) {
-                throw new IllegalStateException("Could not scrub ids");
-            }
-        }
-        this.id = ++id;
-        return id;
-    }
-
     @Override
     protected void wakeup(boolean inEventLoop) {
         if (!inEventLoop && WAKEN_UP_UPDATER.compareAndSet(this, 0, 1)) {
@@ -133,10 +108,9 @@ final class EpollEventLoop extends SingleThreadEventLoop {
      */
     void add(AbstractEpollChannel ch) {
         assert inEventLoop();
-        int id = nextId();
+        int fd = ch.fd().intValue();
-        Native.epollCtlAdd(epollFd, ch.fd().intValue(), ch.flags, id);
+        Native.epollCtlAdd(epollFd, fd, ch.flags);
-        ch.id = id;
+        channels.put(fd, ch);
-        ids.put(id, ch);
     }
 
     /**
@@ -144,7 +118,7 @@ final class EpollEventLoop extends SingleThreadEventLoop {
      */
     void modify(AbstractEpollChannel ch) {
         assert inEventLoop();
-        Native.epollCtlMod(epollFd, ch.fd().intValue(), ch.flags, ch.id);
+        Native.epollCtlMod(epollFd, ch.fd().intValue(), ch.flags);
     }
 
     /**
@@ -152,10 +126,14 @@ final class EpollEventLoop extends SingleThreadEventLoop {
      */
     void remove(AbstractEpollChannel ch) {
         assert inEventLoop();
-        if (ids.remove(ch.id) != null && ch.isOpen()) {
+
-            // Remove the epoll. This is only needed if it's still open as otherwise it will be automatically
+        if (ch.isOpen()) {
-            // removed once the file-descriptor is closed.
+            int fd = ch.fd().intValue();
-            Native.epollCtlDel(epollFd, ch.fd().intValue());
+            if (channels.remove(fd) != null) {
+                // Remove the epoll. This is only needed if it's still open as otherwise it will be automatically
+                // removed once the file-descriptor is closed.
+                Native.epollCtlDel(epollFd, ch.fd().intValue());
+            }
         }
     }
 
@@ -183,7 +161,7 @@ final class EpollEventLoop extends SingleThreadEventLoop {
         this.ioRatio = ioRatio;
     }
 
-    private int epollWait(boolean oldWakenUp) {
+    private int epollWait(boolean oldWakenUp) throws IOException {
         int selectCnt = 0;
         long currentTimeNanos = System.nanoTime();
         long selectDeadLineNanos = currentTimeNanos + delayNanos(currentTimeNanos);
@@ -275,9 +253,9 @@ final class EpollEventLoop extends SingleThreadEventLoop {
                     final long ioTime = System.nanoTime() - ioStartTime;
                     runAllTasks(ioTime * (100 - ioRatio) / ioRatio);
                 }
-                if (allowGrowing && ready == events.length) {
+                if (allowGrowing && ready == events.length()) {
-                    // double the size of the array as we needed the whole space for the events
+                    //increase the size of the array as we needed the whole space for the events
-                    events = new long[events.length << 1];
+                    events.increase();
                 }
                 if (isShuttingDown()) {
                     closeAll();
@@ -300,41 +278,52 @@ final class EpollEventLoop extends SingleThreadEventLoop {
     }
 
     private void closeAll() {
-        Native.epollWait(epollFd, events, 0);
+        try {
-        Collection<AbstractEpollChannel> channels = new ArrayList<AbstractEpollChannel>(ids.size());
+            Native.epollWait(epollFd, events, 0);
+        } catch (IOException ignore) {
+            // ignore on close
+        }
+        Collection<AbstractEpollChannel> array = new ArrayList<AbstractEpollChannel>(channels.size());
 
-        for (IntObjectMap.Entry<AbstractEpollChannel> entry: ids.entries()) {
+        for (IntObjectMap.Entry<AbstractEpollChannel> entry: channels.entries()) {
-            channels.add(entry.value());
+            array.add(entry.value());
         }
 
-        for (AbstractEpollChannel ch: channels) {
+        for (AbstractEpollChannel ch: array) {
             ch.unsafe().close(ch.unsafe().voidPromise());
         }
     }
 
-    private void processReady(long[] events, int ready) {
+    private void processReady(EpollEventArray events, int ready) {
         for (int i = 0; i < ready; i ++) {
-            final long ev = events[i];
+            final int fd = events.fd(i);
-
+            if (fd == eventFd) {
-            int id = (int) (ev >> 32L);
-            if (id == 0) {
                 // consume wakeup event
                 Native.eventFdRead(eventFd);
             } else {
-                AbstractEpollChannel ch = ids.get(id);
+                final long ev = events.events(i);
-                if (ch != null) {
+
+                AbstractEpollChannel ch = channels.get(fd);
+                if (ch != null && ch.isOpen()) {
+                    boolean close = (ev & Native.EPOLLRDHUP) != 0;
+                    boolean read = (ev & Native.EPOLLIN) != 0;
+                    boolean write = (ev & Native.EPOLLOUT) != 0;
+
                     AbstractEpollUnsafe unsafe = (AbstractEpollUnsafe) ch.unsafe();
-                    if ((ev & Native.EPOLLOUT) != 0 && ch.isOpen()) {
+                    if (write) {
                         // force flush of data as the epoll is writable again
                         unsafe.epollOutReady();
                     }
-                    if ((ev & Native.EPOLLIN) != 0 && ch.isOpen()) {
+                    if (read) {
                         // Something is ready to read, so consume it now
                         unsafe.epollInReady();
                     }
-                    if ((ev & Native.EPOLLRDHUP) != 0 && ch.isOpen()) {
+                    if (close) {
                         unsafe.epollRdHupReady();
                     }
+                } else {
+                    // We received an event for an fd which we not use anymore. Remove it from the epoll_event set.
+                    Native.epollCtlDel(epollFd, fd);
                 }
             }
         }
@@ -343,14 +332,19 @@ final class EpollEventLoop extends SingleThreadEventLoop {
     @Override
     protected void cleanup() {
         try {
-            Native.close(epollFd);
+            try {
-        } catch (IOException e) {
+                Native.close(epollFd);
-            logger.warn("Failed to close the epoll fd.", e);
+            } catch (IOException e) {
-        }
+                logger.warn("Failed to close the epoll fd.", e);
-        try {
+            }
-            Native.close(eventFd);
+            try {
-        } catch (IOException e) {
+                Native.close(eventFd);
-            logger.warn("Failed to close the event fd.", e);
+            } catch (IOException e) {
+                logger.warn("Failed to close the event fd.", e);
+            }
+        } finally {
+            // release native memory
+            events.free();
         }
     }
 }

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollSocketChannel.java

@@ -37,6 +37,8 @@ public final class EpollSocketChannel extends AbstractEpollStreamChannel impleme
 
     EpollSocketChannel(Channel parent, int fd) {
         super(parent, fd);
+        // Add EPOLLRDHUP so we are notified once the remote peer close the connection.
+        flags |= Native.EPOLLRDHUP;
         config = new EpollSocketChannelConfig(this);
         // Directly cache the remote and local addresses
         // See https://github.com/netty/netty/issues/2359
@@ -46,6 +48,8 @@ public final class EpollSocketChannel extends AbstractEpollStreamChannel impleme
 
     public EpollSocketChannel() {
         super(Native.socketStreamFd());
+        // Add EPOLLRDHUP so we are notified once the remote peer close the connection.
+        flags |= Native.EPOLLRDHUP;
         config = new EpollSocketChannelConfig(this);
     }
 

transport-native-epoll/src/main/java/io/netty/channel/epoll/Native.java

@@ -49,10 +49,10 @@ final class Native {
     }
 
     // EventLoop operations and constants
-    public static final int EPOLLIN = 0x01;
+    public static final int EPOLLIN = epollin();
-    public static final int EPOLLOUT = 0x02;
+    public static final int EPOLLOUT = epollout();
-    public static final int EPOLLRDHUP = 0x04;
+    public static final int EPOLLRDHUP = epollrdhup();
-    public static final int EPOLLET = 0x08;
+    public static final int EPOLLET = epollet();
 
     public static final int IOV_MAX = iovMax();
     public static final int UIO_MAX_IOV = uioMaxIov();
@@ -134,9 +134,18 @@ final class Native {
     public static native void eventFdWrite(int fd, long value);
     public static native void eventFdRead(int fd);
     public static native int epollCreate();
-    public static native int epollWait(int efd, long[] events, int timeout);
+    public static int epollWait(int efd, EpollEventArray events, int timeout) throws IOException {
-    public static native void epollCtlAdd(int efd, final int fd, final int flags, final int id);
+        int ready = epollWait0(efd, events.memoryAddress(), events.length(), timeout);
-    public static native void epollCtlMod(int efd, final int fd, final int flags, final int id);
+        if (ready < 0) {
+            throw newIOException("epoll_wait", ready);
+        }
+        return ready;
+    }
+    private static native int epollWait0(int efd, long address, int len, int timeout);
+
+    public static native void epollCtlAdd(int efd, final int fd, final int flags);
+
+    public static native void epollCtlMod(int efd, final int fd, final int flags);
     public static native void epollCtlDel(int efd, final int fd);
 
     private static native int errnoEBADF();
@@ -623,6 +632,15 @@ final class Native {
 
     private static native int uioMaxIov();
 
+    // epoll_event related
+    public static native int sizeofEpollEvent();
+    public static native int offsetofEpollData();
+
+    private static native int epollin();
+    private static native int epollout();
+    private static native int epollrdhup();
+    private static native int epollet();
+
     private Native() {
         // utility
     }