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8253478: (se) epoll Selector should use eventfd for wakeup instead of…
… pipe

Reviewed-by: alanb
  • Loading branch information
Brian Burkhalter committed Jan 21, 2021
1 parent 34eb8b3 commit a8073efeedd257d76fe9b31c62b5f556bf78e77d
Showing 4 changed files with 200 additions and 14 deletions.
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2005, 2018, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2005, 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
@@ -58,9 +58,8 @@ class EPollSelectorImpl extends SelectorImpl {
// address of poll array when polling with epoll_wait
private final long pollArrayAddress;

// file descriptors used for interrupt
private final int fd0;
private final int fd1;
// eventfd object used for interrupt
private final EventFD eventfd;

// maps file descriptor to selection key, synchronize on selector
private final Map<Integer, SelectionKeyImpl> fdToKey = new HashMap<>();
@@ -80,17 +79,16 @@ class EPollSelectorImpl extends SelectorImpl {
this.pollArrayAddress = EPoll.allocatePollArray(NUM_EPOLLEVENTS);

try {
long fds = IOUtil.makePipe(false);
this.fd0 = (int) (fds >>> 32);
this.fd1 = (int) fds;
this.eventfd = new EventFD();
IOUtil.configureBlocking(IOUtil.newFD(eventfd.efd()), false);
} catch (IOException ioe) {
EPoll.freePollArray(pollArrayAddress);
FileDispatcherImpl.closeIntFD(epfd);
throw ioe;
}

// register one end of the socket pair for wakeups
EPoll.ctl(epfd, EPOLL_CTL_ADD, fd0, EPOLLIN);
// register the eventfd object for wakeups
EPoll.ctl(epfd, EPOLL_CTL_ADD, eventfd.efd(), EPOLLIN);
}

private void ensureOpen() {
@@ -188,7 +186,7 @@ private int processEvents(int numEntries, Consumer<SelectionKey> action)
for (int i=0; i<numEntries; i++) {
long event = EPoll.getEvent(pollArrayAddress, i);
int fd = EPoll.getDescriptor(event);
if (fd == fd0) {
if (fd == eventfd.efd()) {
interrupted = true;
} else {
SelectionKeyImpl ski = fdToKey.get(fd);
@@ -218,8 +216,7 @@ protected void implClose() throws IOException {
FileDispatcherImpl.closeIntFD(epfd);
EPoll.freePollArray(pollArrayAddress);

FileDispatcherImpl.closeIntFD(fd0);
FileDispatcherImpl.closeIntFD(fd1);
eventfd.close();
}

@Override
@@ -251,7 +248,7 @@ public Selector wakeup() {
synchronized (interruptLock) {
if (!interruptTriggered) {
try {
IOUtil.write1(fd1, (byte)0);
eventfd.set();
} catch (IOException ioe) {
throw new InternalError(ioe);
}
@@ -263,7 +260,7 @@ public Selector wakeup() {

private void clearInterrupt() throws IOException {
synchronized (interruptLock) {
IOUtil.drain(fd0);
eventfd.reset();
interruptTriggered = false;
}
}
@@ -0,0 +1,73 @@
/*
* 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. 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;

/*
* Provides access to the Linux eventfd object.
*/
final class EventFD {
private final int efd;

/**
* Creates a blocking eventfd object with initial value zero.
*/
EventFD() throws IOException {
efd = eventfd0();
}

int efd() {
return efd;
}

void set() throws IOException {
set0(efd);
}

void reset() throws IOException {
IOUtil.drain(efd);
}

void close() throws IOException {
FileDispatcherImpl.closeIntFD(efd);
}

private static native int eventfd0() throws IOException;

/**
* Writes the value 1 to the eventfd object as a long in the
* native byte order of the platform.
*
* @param the integral eventfd file descriptor
* @return the number of bytes written; should equal 8
*/
private static native int set0(int efd) throws IOException;

static {
IOUtil.load();
}
}
@@ -0,0 +1,54 @@
/*
* 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. 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 <sys/eventfd.h>

#include "jni.h"
#include "jni_util.h"
#include "jvm.h"
#include "jlong.h"
#include "nio.h"
#include "nio_util.h"

#include "sun_nio_ch_EventFD.h"

JNIEXPORT jint JNICALL
Java_sun_nio_ch_EventFD_eventfd0(JNIEnv *env, jclass klazz)
{
int efd = eventfd((uint64_t)0, 0);
if (efd == -1) {
JNU_ThrowIOExceptionWithLastError(env, "eventfd failed");
return IOS_THROWN;
}
return efd;
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_EventFD_set0(JNIEnv *env, jclass klazz, jint efd)
{
long one = 1L;
return convertReturnVal(env, write(efd, (void*)&one, sizeof(long)),
JNI_FALSE);
}
@@ -0,0 +1,62 @@
/*
* Copyright (c) 2014, Oracle America, Inc.
* 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.
*
* * Neither the name of Oracle nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* 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 HOLDER 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.
*/

package org.openjdk.bench.java.nio;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;

import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;

/**
* Benchmark for the Selector wakeup mechanism. Intended primarily for the
* epoll(7)-based implementation on Linux.
*/
@State(Scope.Thread)
public class SelectorWakeup {
private Selector sel;

@Setup(Level.Iteration)
public void setup() throws IOException {
sel = Selector.open();
}

@Benchmark
public int test() throws IOException {
return sel.wakeup().select();
}
}

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