8266369: (se) Add wepoll based Selector

Reviewed-by: chegar, michaelm, vtewari, dfuchs, bpb

src/java.base/share/classes/sun/nio/ch/Net.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -679,6 +679,10 @@ public class Net {
      */
     static native int sendOOB(FileDescriptor fd, byte data) throws IOException;
 
+    /**
+     * Read and discard urgent data (MSG_OOB) on the socket.
+     */
+    static native boolean discardOOB(FileDescriptor fd) throws IOException;
 
     // -- Multicast support --
 

src/java.base/share/classes/sun/nio/ch/SelectionKeyImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,7 @@
 
 package sun.nio.ch;
 
+import java.io.FileDescriptor;
 import java.lang.invoke.ConstantBootstraps;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.VarHandle;
@@ -74,6 +75,10 @@ public final class SelectionKeyImpl
             throw new CancelledKeyException();
     }
 
+    FileDescriptor getFD() {
+        return channel.getFD();
+    }
+
     int getFDVal() {
         return channel.getFDVal();
     }

src/java.base/windows/classes/sun/nio/ch/DefaultSelectorProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -35,7 +35,7 @@ import java.security.PrivilegedAction;
 public class DefaultSelectorProvider {
     private static final SelectorProviderImpl INSTANCE;
     static {
-        PrivilegedAction<SelectorProviderImpl> pa = WindowsSelectorProvider::new;
+        PrivilegedAction<SelectorProviderImpl> pa = WEPollSelectorProvider::new;
         INSTANCE = AccessController.doPrivileged(pa);
     }
 

src/java.base/windows/classes/sun/nio/ch/PipeImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -61,10 +61,10 @@ class PipeImpl
     private static final Random RANDOM_NUMBER_GENERATOR = new SecureRandom();
 
     // Source and sink channels
-    private final SourceChannel source;
+    private final SourceChannelImpl source;
-    private final SinkChannel sink;
+    private final SinkChannelImpl sink;
 
-    private class Initializer
+    private static class Initializer
         implements PrivilegedExceptionAction<Void>
     {
 
@@ -203,11 +203,11 @@ class PipeImpl
         this.sink = initializer.sink;
     }
 
-    public SourceChannel source() {
+    public SourceChannelImpl source() {
         return source;
     }
 
-    public SinkChannel sink() {
+    public SinkChannelImpl sink() {
         return sink;
     }
 

src/java.base/windows/classes/sun/nio/ch/WEPoll.java

@@ -0,0 +1,146 @@
+/*
+ * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package sun.nio.ch;
+
+import java.io.IOException;
+import jdk.internal.misc.Unsafe;
+
+/**
+ * Provides access to wepoll.
+ */
+class WEPoll {
+    private static final Unsafe UNSAFE = Unsafe.getUnsafe();
+    private static final int ADDRESS_SIZE = UNSAFE.addressSize();
+
+    private WEPoll() { }
+
+    /**
+     * typedef union epoll_data {
+     *     void *ptr;
+     *     int fd;
+     *     uint32_t u32;
+     *     uint64_t u64;
+     *     SOCKET sock;   // Windows specific
+     *     HANDLE hnd;    // Windows specific
+     *  } epoll_data_t;
+     *
+     * struct epoll_event {
+     *     uint32_t events;
+     *     epoll_data_t data;
+     * }
+     */
+    private static final int SIZEOF_EPOLLEVENT   = eventSize();
+    private static final int OFFSETOF_EVENTS     = eventsOffset();
+    private static final int OFFSETOF_SOCK       = dataOffset();
+
+    // opcodes
+    static final int EPOLL_CTL_ADD  = 1;
+    static final int EPOLL_CTL_MOD  = 2;
+    static final int EPOLL_CTL_DEL  = 3;
+
+    // events
+    static final int EPOLLIN   = (1 << 0);
+    static final int EPOLLPRI  = (1 << 1);
+    static final int EPOLLOUT  = (1 << 2);
+    static final int EPOLLERR  = (1 << 3);
+    static final int EPOLLHUP  = (1 << 4);
+
+    // flags
+    static final int EPOLLONESHOT = (1 << 31);
+
+    /**
+     * Allocates a poll array to handle up to {@code count} events.
+     */
+    static long allocatePollArray(int count) {
+        long size = (long) count * SIZEOF_EPOLLEVENT;
+        long base = UNSAFE.allocateMemory(size);
+        UNSAFE.setMemory(base, size, (byte) 0);
+        return base;
+    }
+
+    /**
+     * Free a poll array
+     */
+    static void freePollArray(long address) {
+        UNSAFE.freeMemory(address);
+    }
+
+    /**
+     * Returns event[i];
+     */
+    static long getEvent(long address, int i) {
+        return address + (SIZEOF_EPOLLEVENT*i);
+    }
+
+    /**
+     * Returns event->data.socket
+     */
+    static long getSocket(long eventAddress) {
+        if (ADDRESS_SIZE == 8) {
+            return UNSAFE.getLong(eventAddress + OFFSETOF_SOCK);
+        } else {
+            return UNSAFE.getInt(eventAddress + OFFSETOF_SOCK);
+        }
+    }
+
+    /**
+     * Return event->data.socket as an int file descriptor
+     */
+    static int getDescriptor(long eventAddress) {
+        long s = getSocket(eventAddress);
+        int fd = (int) s;
+        assert ((long) fd) == s;
+        return fd;
+    }
+
+    /**
+     * Returns event->events
+     */
+    static int getEvents(long eventAddress) {
+        return UNSAFE.getInt(eventAddress + OFFSETOF_EVENTS);
+    }
+
+    // -- Native methods --
+
+    private static native int eventSize();
+
+    private static native int eventsOffset();
+
+    private static native int dataOffset();
+
+    static native long create() throws IOException;
+
+    static native int ctl(long h, int opcode, long s, int events);
+
+    static native int wait(long h, long pollAddress, int numfds, int timeout)
+        throws IOException;
+
+    static native void close(long h);
+
+    static {
+        IOUtil.load();
+    }
+}

src/java.base/windows/classes/sun/nio/ch/WEPollSelectorImpl.java

@@ -0,0 +1,276 @@
+/*
+ * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package sun.nio.ch;
+
+import java.io.FileDescriptor;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.ClosedSelectorException;
+import java.nio.channels.Pipe;
+import java.nio.channels.SelectionKey;
+import java.nio.channels.Selector;
+import java.nio.channels.spi.SelectorProvider;
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Consumer;
+
+import static sun.nio.ch.WEPoll.*;
+
+/**
+ * Windows wepoll based Selector implementation
+ */
+class WEPollSelectorImpl extends SelectorImpl {
+    // maximum number of events to poll in one call to epoll_wait
+    private static final int NUM_EPOLLEVENTS = 256;
+
+    // wepoll handle
+    private final long eph;
+
+    // address of epoll_event array when polling with epoll_wait
+    private final long pollArrayAddress;
+
+    // maps SOCKET to selection key, synchronize on selector
+    private final Map<Integer, SelectionKeyImpl> fdToKey = new HashMap<>();
+
+    // pending new registrations/updates, queued by setEventOps
+    private final Object updateLock = new Object();
+    private final Deque<SelectionKeyImpl> updateKeys = new ArrayDeque<>();
+
+    // interrupt/wakeup
+    private final Object interruptLock = new Object();
+    private boolean interruptTriggered;
+    private final PipeImpl pipe;
+    private final int fd0Val, fd1Val;
+
+    WEPollSelectorImpl(SelectorProvider sp) throws IOException {
+        super(sp);
+
+        this.eph = WEPoll.create();
+        this.pollArrayAddress = WEPoll.allocatePollArray(NUM_EPOLLEVENTS);
+
+        // wakeup support
+        try {
+            this.pipe = new PipeImpl(sp, /*buffering*/ false);
+        } catch (IOException ioe) {
+            WEPoll.freePollArray(pollArrayAddress);
+            WEPoll.close(eph);
+            throw ioe;
+        }
+        this.fd0Val = pipe.source().getFDVal();
+        this.fd1Val = pipe.sink().getFDVal();
+
+        // register one end of the pipe for wakeups
+        WEPoll.ctl(eph, EPOLL_CTL_ADD, fd0Val, WEPoll.EPOLLIN);
+    }
+
+    private void ensureOpen() {
+        if (!isOpen())
+            throw new ClosedSelectorException();
+    }
+
+    @Override
+    protected int doSelect(Consumer<SelectionKey> action, long timeout)
+        throws IOException
+    {
+        assert Thread.holdsLock(this);
+
+        // epoll_wait timeout is int
+        int to = (int) Math.min(timeout, Integer.MAX_VALUE);
+        boolean blocking = (to != 0);
+
+        int numEntries;
+        processUpdateQueue();
+        processDeregisterQueue();
+        try {
+            begin(blocking);
+            numEntries = WEPoll.wait(eph, pollArrayAddress, NUM_EPOLLEVENTS, to);
+        } finally {
+            end(blocking);
+        }
+        processDeregisterQueue();
+        return processEvents(numEntries, action);
+    }
+
+    /**
+     * Process changes to the interest ops.
+     */
+    private void processUpdateQueue() {
+        assert Thread.holdsLock(this);
+
+        synchronized (updateLock) {
+            SelectionKeyImpl ski;
+            while ((ski = updateKeys.pollFirst()) != null) {
+                if (ski.isValid()) {
+                    int fd = ski.getFDVal();
+                    // add to fdToKey if needed
+                    SelectionKeyImpl previous = fdToKey.putIfAbsent(fd, ski);
+                    assert (previous == null) || (previous == ski);
+                    int newOps = ski.translateInterestOps();
+                    int registeredOps = ski.registeredEvents();
+                    if (newOps != registeredOps) {
+                        if (newOps == 0) {
+                            // remove from epoll
+                            WEPoll.ctl(eph, EPOLL_CTL_DEL, fd, 0);
+                        } else {
+                            int events = toEPollEvents(newOps);
+                            if (registeredOps == 0) {
+                                // add to epoll
+                                WEPoll.ctl(eph, EPOLL_CTL_ADD, fd, events);
+                            } else {
+                                // modify events
+                                WEPoll.ctl(eph, EPOLL_CTL_MOD, fd, events);
+                            }
+                        }
+                        ski.registeredEvents(newOps);
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * Process the polled events.
+     * If the interrupt fd has been selected, drain it and clear the interrupt.
+     */
+    private int processEvents(int numEntries, Consumer<SelectionKey> action)
+        throws IOException
+    {
+        assert Thread.holdsLock(this);
+
+        boolean interrupted = false;
+        int numKeysUpdated = 0;
+        for (int i = 0; i < numEntries; i++) {
+            long event = WEPoll.getEvent(pollArrayAddress, i);
+            int fd = WEPoll.getDescriptor(event);
+            if (fd == fd0Val) {
+                interrupted = true;
+            } else {
+                SelectionKeyImpl ski = fdToKey.get(fd);
+                if (ski != null) {
+                    int events = WEPoll.getEvents(event);
+                    if ((events & WEPoll.EPOLLPRI) != 0) {
+                        Net.discardOOB(ski.getFD());
+                    }
+                    int rOps = toReadyOps(events);
+                    numKeysUpdated += processReadyEvents(rOps, ski, action);
+                }
+            }
+        }
+
+        if (interrupted) {
+            clearInterrupt();
+        }
+
+        return numKeysUpdated;
+    }
+
+    @Override
+    protected void implClose() throws IOException {
+        assert !isOpen() && Thread.holdsLock(this);
+
+        // prevent further wakeup
+        synchronized (interruptLock) {
+            interruptTriggered = true;
+        }
+
+        // close the epoll port and free resources
+        WEPoll.close(eph);
+        WEPoll.freePollArray(pollArrayAddress);
+        pipe.sink().close();
+        pipe.source().close();
+    }
+
+    @Override
+    protected void implDereg(SelectionKeyImpl ski) throws IOException {
+        assert !ski.isValid() && Thread.holdsLock(this);
+
+        int fd = ski.getFDVal();
+        if (fdToKey.remove(fd) != null) {
+            if (ski.registeredEvents() != 0) {
+                WEPoll.ctl(eph, EPOLL_CTL_DEL, fd, 0);
+                ski.registeredEvents(0);
+            }
+        } else {
+            assert ski.registeredEvents() == 0;
+        }
+    }
+
+    @Override
+    public void setEventOps(SelectionKeyImpl ski) {
+        ensureOpen();
+        synchronized (updateLock) {
+            updateKeys.addLast(ski);
+        }
+    }
+
+    @Override
+    public Selector wakeup() {
+        synchronized (interruptLock) {
+            if (!interruptTriggered) {
+                try {
+                    IOUtil.write1(fd1Val, (byte) 0);
+                } catch (IOException ioe) {
+                    throw new InternalError(ioe);
+                }
+                interruptTriggered = true;
+            }
+        }
+        return this;
+    }
+
+    private void clearInterrupt() throws IOException {
+        synchronized (interruptLock) {
+            IOUtil.drain(fd0Val);
+            interruptTriggered = false;
+        }
+    }
+
+    /**
+     * Maps interest ops to epoll events
+     */
+    private static int toEPollEvents(int ops) {
+        int events = EPOLLPRI;
+        if ((ops & Net.POLLIN) != 0)
+            events |= EPOLLIN;
+        if ((ops & (Net.POLLOUT | Net.POLLCONN)) != 0)
+            events |= EPOLLOUT;
+        return events;
+    }
+
+    /**
+     * Map epoll events to ready ops
+     */
+    private static int toReadyOps(int events) {
+        int ops = 0;
+        if ((events & WEPoll.EPOLLIN) != 0) ops |= Net.POLLIN;
+        if ((events & WEPoll.EPOLLOUT) != 0) ops |= (Net.POLLOUT | Net.POLLCONN);
+        if ((events & WEPoll.EPOLLHUP) != 0) ops |= Net.POLLHUP;
+        if ((events & WEPoll.EPOLLERR) != 0) ops |= Net.POLLERR;
+        return ops;
+    }
+}

src/java.base/windows/classes/sun/nio/ch/WEPollSelectorProvider.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package sun.nio.ch;
+
+import java.io.IOException;
+import java.nio.channels.spi.AbstractSelector;
+
+public class WEPollSelectorProvider extends SelectorProviderImpl {
+    public AbstractSelector openSelector() throws IOException {
+        return new WEPollSelectorImpl(this);
+    }
+}

src/java.base/windows/classes/sun/nio/ch/WindowsSelectorImpl.java

@@ -365,7 +365,9 @@ class WindowsSelectorImpl extends SelectorImpl {
         private native int poll0(long pollAddress, int numfds,
              int[] readFds, int[] writeFds, int[] exceptFds, long timeout, long fdsBuffer);
 
-        private int processSelectedKeys(long updateCount, Consumer<SelectionKey> action) {
+        private int processSelectedKeys(long updateCount, Consumer<SelectionKey> action)
+            throws IOException
+        {
             int numKeysUpdated = 0;
             numKeysUpdated += processFDSet(updateCount, action, readFds,
                                            Net.POLLIN,
@@ -392,6 +394,7 @@ class WindowsSelectorImpl extends SelectorImpl {
                                  Consumer<SelectionKey> action,
                                  int[] fds, int rOps,
                                  boolean isExceptFds)
+            throws IOException
         {
             int numKeysUpdated = 0;
             for (int i = 1; i <= fds[0]; i++) {
@@ -415,7 +418,7 @@ class WindowsSelectorImpl extends SelectorImpl {
                 SelectableChannel sc = ski.channel();
                 if (isExceptFds && (sc instanceof SocketChannelImpl)
                         && ((SocketChannelImpl) sc).isNetSocket()
-                        && discardUrgentData(desc)) {
+                        && Net.discardOOB(ski.getFD())) {
                     continue;
                 }
 
@@ -511,8 +514,6 @@ class WindowsSelectorImpl extends SelectorImpl {
 
     private native void resetWakeupSocket0(int wakeupSourceFd);
 
-    private native boolean discardUrgentData(int fd);
-
     // We increment this counter on each call to updateSelectedKeys()
     // each entry in  SubSelector.fdsMap has a memorized value of
     // updateCount. When we increment numKeysUpdated we set updateCount
@@ -523,7 +524,7 @@ class WindowsSelectorImpl extends SelectorImpl {
 
     // Update ops of the corresponding Channels. Add the ready keys to the
     // ready queue.
-    private int updateSelectedKeys(Consumer<SelectionKey> action) {
+    private int updateSelectedKeys(Consumer<SelectionKey> action) throws IOException {
         updateCount++;
         int numKeysUpdated = 0;
         numKeysUpdated += subSelector.processSelectedKeys(updateCount, action);

src/java.base/windows/legal/wepoll.md

@@ -0,0 +1,34 @@
+## Bert Belder: wepoll v 1.5.8
+
+### wepoll License
+```
+wepoll - epoll for Windows
+https://github.com/piscisaureus/wepoll
+
+Copyright 2012-2020, Bert Belder <bertbelder@gmail.com>
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+  * Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+```

src/java.base/windows/native/libnio/ch/IOUtil.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -148,45 +148,36 @@ Java_sun_nio_ch_IOUtil_configureBlocking(JNIEnv *env, jclass clazz,
     }
 }
 
-/* Note: Drain uses the int fd value. It is currently not called
-   on windows.
-*/
 JNIEXPORT jboolean JNICALL
 Java_sun_nio_ch_IOUtil_drain(JNIEnv *env, jclass cl, jint fd)
 {
-    DWORD read = 0;
+    char buf[16];
-    int totalRead = 0;
+    jboolean readBytes = JNI_FALSE;
-    BOOL result = 0;
-    HANDLE h = (HANDLE)_get_osfhandle(fd);
-    char buf[128];
-
-    if (h == INVALID_HANDLE_VALUE) {
-        JNU_ThrowIOExceptionWithLastError(env, "Read failed");
-        return JNI_FALSE;
-    }
-
     for (;;) {
-        result = ReadFile(h,          /* File handle to read */
+        int n = recv((SOCKET) fd, buf, sizeof(buf), 0);
-                          (LPVOID)&buf,    /* address to put data */
+        if (n == SOCKET_ERROR) {
-                          128,        /* number of bytes to read */
+            if (WSAGetLastError() != WSAEWOULDBLOCK) {
-                          &read,      /* number of bytes read */
+                JNU_ThrowIOExceptionWithLastError(env, "recv failed");
-                          NULL);      /* no overlapped struct */
-
-        if (result == 0) {
-            int error = GetLastError();
-            if (error == ERROR_NO_DATA) {
-                return (totalRead > 0) ? JNI_TRUE : JNI_FALSE;
             }
-            JNU_ThrowIOExceptionWithLastError(env, "Drain");
+            return readBytes;
-            return JNI_FALSE;
-        }
-        if (read > 0) {
-            totalRead += read;
-        } else {
-            break;
         }
+        if (n <= 0)
+            return readBytes;
+        if (n < (int)sizeof(buf))
+            return JNI_TRUE;
+        readBytes = JNI_TRUE;
     }
-    return (totalRead > 0) ? JNI_TRUE : JNI_FALSE;
+}
+
+JNIEXPORT jint JNICALL
+Java_sun_nio_ch_IOUtil_write1(JNIEnv *env, jclass cl, jint fd, jbyte b)
+{
+    int n = send((SOCKET) fd, &b, 1, 0);
+    if (n == SOCKET_ERROR && WSAGetLastError() != WSAEWOULDBLOCK) {
+        JNU_ThrowIOExceptionWithLastError(env, "send failed");
+        return IOS_THROWN;
+    }
+    return (n == 1) ? 1 : 0;
 }
 
 /* Note: This function returns the int fd value from file descriptor.

src/java.base/windows/native/libnio/ch/Net.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -654,8 +654,7 @@ Java_sun_nio_ch_Net_poll(JNIEnv* env, jclass this, jobject fdo, jint events, jlo
     if (events & POLLIN) {
         FD_SET(fd, &rd);
     }
-    if (events & POLLOUT ||
+    if (events & POLLOUT) {
-        events & POLLCONN) {
         FD_SET(fd, &wr);
     }
     FD_SET(fd, &ex);
@@ -768,7 +767,7 @@ Java_sun_nio_ch_Net_pollnvalValue(JNIEnv *env, jclass this)
 JNIEXPORT jshort JNICALL
 Java_sun_nio_ch_Net_pollconnValue(JNIEnv *env, jclass this)
 {
-    return (jshort)POLLCONN;
+    return (jshort)POLLOUT;
 }
 
 JNIEXPORT jint JNICALL
@@ -786,3 +785,24 @@ Java_sun_nio_ch_Net_sendOOB(JNIEnv* env, jclass this, jobject fdo, jbyte b)
         return n;
     }
 }
+
+JNIEXPORT jboolean JNICALL
+Java_sun_nio_ch_Net_discardOOB(JNIEnv* env, jclass clazz, jobject fdo)
+{
+    char buf[8];
+    jboolean discarded = JNI_FALSE;
+    for (;;) {
+        int n = recv(fdval(env, fdo), (char*)&buf, sizeof(buf), MSG_OOB);
+        if (n == SOCKET_ERROR) {
+            if (WSAGetLastError() != WSAEWOULDBLOCK) {
+                JNU_ThrowIOExceptionWithLastError(env, "recv failed");
+            }
+            return discarded;
+        }
+        if (n <= 0)
+            return discarded;
+        if (n < (int)sizeof(buf))
+            return JNI_TRUE;
+        discarded = JNI_TRUE;
+    }
+}

src/java.base/windows/native/libnio/ch/WEPollNatives.c

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include "jni.h"
+#include "jni_util.h"
+#include "jvm.h"
+#include "jlong.h"
+#include "nio.h"
+#include "nio_util.h"
+#include "wepoll.h"
+#include "sun_nio_ch_WEPoll.h"
+
+JNIEXPORT jint JNICALL
+Java_sun_nio_ch_WEPoll_eventSize(JNIEnv* env, jclass clazz)
+{
+    return sizeof(struct epoll_event);
+}
+
+JNIEXPORT jint JNICALL
+Java_sun_nio_ch_WEPoll_eventsOffset(JNIEnv* env, jclass clazz)
+{
+    return offsetof(struct epoll_event, events);
+}
+
+JNIEXPORT jint JNICALL
+Java_sun_nio_ch_WEPoll_dataOffset(JNIEnv* env, jclass clazz)
+{
+    return offsetof(struct epoll_event, data);
+}
+
+JNIEXPORT jlong JNICALL
+Java_sun_nio_ch_WEPoll_create(JNIEnv *env, jclass clazz) {
+    HANDLE h = epoll_create1(0);
+    if (h == NULL) {
+        JNU_ThrowIOExceptionWithLastError(env, "epoll_create1 failed");
+    }
+    return ptr_to_jlong(h);
+}
+
+JNIEXPORT jint JNICALL
+Java_sun_nio_ch_WEPoll_ctl(JNIEnv *env, jclass clazz, jlong h,
+                           jint opcode, jlong s, jint events)
+{
+    struct epoll_event event;
+    int res;
+    SOCKET socket = (SOCKET) jlong_to_ptr(s);
+
+    event.events = (uint32_t) events;
+    event.data.sock = socket;
+
+    res = epoll_ctl(jlong_to_ptr(h), opcode, socket, &event);
+    return (res == 0) ? 0 : errno;
+}
+
+JNIEXPORT jint JNICALL
+Java_sun_nio_ch_WEPoll_wait(JNIEnv *env, jclass clazz, jlong h,
+                            jlong address, jint numfds, jint timeout)
+{
+    struct epoll_event *events = jlong_to_ptr(address);
+    int res = epoll_wait(jlong_to_ptr(h), events, numfds, timeout);
+    if (res < 0) {
+        JNU_ThrowIOExceptionWithLastError(env, "epoll_wait failed");
+        return IOS_THROWN;
+    }
+    return res;
+}
+
+JNIEXPORT void JNICALL
+Java_sun_nio_ch_WEPoll_close(JNIEnv *env, jclass clazz, jlong h) {
+    epoll_close(jlong_to_ptr(h));
+}

src/java.base/windows/native/libnio/ch/WindowsSelectorImpl.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -99,8 +99,7 @@ Java_sun_nio_ch_WindowsSelectorImpl_00024SubSelector_poll0(JNIEnv *env, jobject
            readfds->fd_array[read_count] = fds[i].fd;
            read_count++;
         }
-        if (fds[i].events & (POLLOUT | POLLCONN))
+        if (fds[i].events & POLLOUT) {
-        {
            writefds->fd_array[write_count] = fds[i].fd;
            write_count++;
         }
@@ -190,19 +189,3 @@ Java_sun_nio_ch_WindowsSelectorImpl_resetWakeupSocket0(JNIEnv *env, jclass this,
         recv(scinFd, bytes, WAKEUP_SOCKET_BUF_SIZE, 0);
     }
 }
-
-JNIEXPORT jboolean JNICALL
-Java_sun_nio_ch_WindowsSelectorImpl_discardUrgentData(JNIEnv* env, jobject this,
-                                                      jint s)
-{
-    char data[8];
-    jboolean discarded = JNI_FALSE;
-    int n;
-    do {
-        n = recv(s, (char*)&data, sizeof(data), MSG_OOB);
-        if (n > 0) {
-            discarded = JNI_TRUE;
-        }
-    } while (n > 0);
-    return discarded;
-}

src/java.base/windows/native/libnio/ch/nio_util.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -64,22 +64,6 @@ struct iovec {
 
 #endif
 
-#ifndef POLLIN
-    /* WSAPoll()/WSAPOLLFD and the corresponding constants are only defined   */
-    /* in Windows Vista / Windows Server 2008 and later. If we are on an      */
-    /* older release we just use the Solaris constants as this was previously */
-    /* done in PollArrayWrapper.java.                                         */
-    #define POLLIN       0x0001
-    #define POLLOUT      0x0004
-    #define POLLERR      0x0008
-    #define POLLHUP      0x0010
-    #define POLLNVAL     0x0020
-    #define POLLCONN     0x0002
-#else
-    /* POLLCONN must not equal any of the other constants (see winsock2.h).   */
-    #define POLLCONN     0x2000
-#endif
-
 /* Defined in UnixDomainSockets.c */
 
 jbyteArray sockaddrToUnixAddressBytes(JNIEnv *env, struct sockaddr_un *sa, socklen_t len);

src/java.base/windows/native/libnio/ch/wepoll.h

@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file and, per its terms, should not be removed:
+ *
+ * wepoll - epoll for Windows
+ * https://github.com/piscisaureus/wepoll
+ *
+ * Copyright 2012-2020, Bert Belder <bertbelder@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef WEPOLL_H_
+#define WEPOLL_H_
+
+#ifndef WEPOLL_EXPORT
+#define WEPOLL_EXPORT
+#endif
+
+#include <stdint.h>
+
+enum EPOLL_EVENTS {
+  EPOLLIN      = (int) (1U <<  0),
+  EPOLLPRI     = (int) (1U <<  1),
+  EPOLLOUT     = (int) (1U <<  2),
+  EPOLLERR     = (int) (1U <<  3),
+  EPOLLHUP     = (int) (1U <<  4),
+  EPOLLRDNORM  = (int) (1U <<  6),
+  EPOLLRDBAND  = (int) (1U <<  7),
+  EPOLLWRNORM  = (int) (1U <<  8),
+  EPOLLWRBAND  = (int) (1U <<  9),
+  EPOLLMSG     = (int) (1U << 10), /* Never reported. */
+  EPOLLRDHUP   = (int) (1U << 13),
+  EPOLLONESHOT = (int) (1U << 31)
+};
+
+#define EPOLLIN      (1U <<  0)
+#define EPOLLPRI     (1U <<  1)
+#define EPOLLOUT     (1U <<  2)
+#define EPOLLERR     (1U <<  3)
+#define EPOLLHUP     (1U <<  4)
+#define EPOLLRDNORM  (1U <<  6)
+#define EPOLLRDBAND  (1U <<  7)
+#define EPOLLWRNORM  (1U <<  8)
+#define EPOLLWRBAND  (1U <<  9)
+#define EPOLLMSG     (1U << 10)
+#define EPOLLRDHUP   (1U << 13)
+#define EPOLLONESHOT (1U << 31)
+
+#define EPOLL_CTL_ADD 1
+#define EPOLL_CTL_MOD 2
+#define EPOLL_CTL_DEL 3
+
+typedef void* HANDLE;
+typedef uintptr_t SOCKET;
+
+typedef union epoll_data {
+  void* ptr;
+  int fd;
+  uint32_t u32;
+  uint64_t u64;
+  SOCKET sock; /* Windows specific */
+  HANDLE hnd;  /* Windows specific */
+} epoll_data_t;
+
+struct epoll_event {
+  uint32_t events;   /* Epoll events and flags */
+  epoll_data_t data; /* User data variable */
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+WEPOLL_EXPORT HANDLE epoll_create(int size);
+WEPOLL_EXPORT HANDLE epoll_create1(int flags);
+
+WEPOLL_EXPORT int epoll_close(HANDLE ephnd);
+
+WEPOLL_EXPORT int epoll_ctl(HANDLE ephnd,
+                            int op,
+                            SOCKET sock,
+                            struct epoll_event* event);
+
+WEPOLL_EXPORT int epoll_wait(HANDLE ephnd,
+                             struct epoll_event* events,
+                             int maxevents,
+                             int timeout);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* WEPOLL_H_ */

test/jdk/java/nio/channels/Selector/ChangingInterests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -27,6 +27,11 @@
  * @summary Test that Selector doesn't spin when changing interest ops
  */
 
+/* @test
+ * @requires (os.family == "windows")
+ * @run main/othervm -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.WindowsSelectorProvider ChangingInterests
+ */
+
 import java.net.*;
 import java.nio.ByteBuffer;
 import java.nio.channels.*;

test/jdk/java/nio/channels/Selector/LotsOfChannels.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -29,6 +29,11 @@
  * @author kladko
  */
 
+/* @test
+ * @requires (os.family == "windows")
+ * @run main/othervm -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.WindowsSelectorProvider LotsOfChannels
+ */
+
 import java.net.*;
 import java.io.*;
 import java.nio.*;

test/jdk/java/nio/channels/Selector/OutOfBand.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -23,11 +23,12 @@
 
 /* @test
  * @bug 6213702
- * @requires (os.family != "mac") | (os.version == "10.10.5")
+ * @summary OOB data causes a SocketChannel, with OOBINLINE disabled, to be selected
- *    | (os.simpleVersion != "10.8" & os.simpleVersion != "10.9"
+ */
- *        & os.simpleVersion != "10.10")
+
- * @summary OOB data causes a SocketChannel, with OOBINLINE disabled, to be
+/* @test
- *    selected
+ * @requires (os.family == "windows")
+ * @run main/othervm -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.WindowsSelectorProvider OutOfBand
  */
 
 import java.net.*;

test/jdk/java/nio/channels/Selector/RacyDeregister.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -39,6 +39,12 @@ import java.nio.channels.SocketChannel;
  * @author Frank Ding
  * @run main/timeout=1200 RacyDeregister
  */
+
+/* @test
+ * @requires (os.family == "windows")
+ * @run main/othervm/timeout=1200 -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.WindowsSelectorProvider RacyDeregister
+ */
+
 public class RacyDeregister {
 
     // 90% of 1200 second timeout as milliseconds

test/jdk/java/nio/channels/Selector/SelectWithConsumer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -22,10 +22,14 @@
  */
 
 /* @test
+ * @summary Unit test for Selector.select/selectNow(Consumer)
  * @bug 8199433 8208780
  * @run testng SelectWithConsumer
- * @summary Unit test for Selector select(Consumer), select(Consumer,long) and
+ */
- *          selectNow(Consumer)
+
+/* @test
+ * @requires (os.family == "windows")
+ * @run testng/othervm -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.WindowsSelectorProvider SelectWithConsumer
  */
 
 import java.io.Closeable;

test/micro/org/openjdk/bench/java/nio/channels/SelectOne.java

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package org.openjdk.bench.java.nio.channels;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.Selector;
+import java.nio.channels.SelectionKey;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Benchmark for Selector.select(Consumer) when there is one channel ready.
+ */
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Thread)
+public class SelectOne {
+    private Selector sel;
+    private List<SocketChannel> clients;
+    private List<SocketChannel> peers;
+
+    private final int nready = 1;  // one channel ready for reading
+
+    @Param({"1", "10", "100", "1000", "10000"})
+    private int nchannels;  // number of registered channels
+
+    @Setup
+    public void setup() throws IOException {
+        sel = Selector.open();
+        clients = new ArrayList<SocketChannel>();
+        peers = new ArrayList<SocketChannel>();
+
+        try (ServerSocketChannel listener = ServerSocketChannel.open()) {
+            InetAddress loopback = InetAddress.getLoopbackAddress();
+            listener.bind(new InetSocketAddress(loopback, 0));
+
+            SocketAddress remote = listener.getLocalAddress();
+            for (int i = 0; i < nchannels; i++) {
+                SocketChannel sc = SocketChannel.open(remote);
+                sc.configureBlocking(false);
+                sc.register(sel, SelectionKey.OP_READ);
+                clients.add(sc);
+
+                SocketChannel peer = listener.accept();
+                peers.add(peer);
+            }
+
+            for (int i = nready - 1; i >= 0; i--) {
+                SocketChannel peer = peers.get(i);
+                peer.write(ByteBuffer.allocate(1));
+            }
+        }
+    }
+
+    @TearDown
+    public void teardown() throws IOException {
+        for (SocketChannel sc: clients) {
+            sc.close();
+        }
+        for (SocketChannel sc: peers) {
+            sc.close();
+        }
+        if (sel != null) {
+            sel.close();
+        }
+    }
+
+    @Benchmark
+    public void testSelectOne() throws IOException {
+        int nselected = sel.select(k -> { });
+        if (nselected != 1) {
+            throw new RuntimeException();
+        }
+    }
+}

test/micro/org/openjdk/bench/java/nio/channels/SelectorWakeup.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, Oracle America, Inc.
+ * Copyright (c) 2021, Oracle America, Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -29,7 +29,7 @@
  * THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-package org.openjdk.bench.java.nio;
+package org.openjdk.bench.java.nio.channels;
 
 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.Level;