3a96e7373b
Motivation: Add an option (through a SelectStrategy return code) to have the Netty event loop thread to do busy-wait on the epoll. The reason for this change is to avoid the context switch cost that comes when the event loop thread is blocked on the epoll_wait() call. On average, the context switch has a penalty of ~13usec. This benefits both: The latency when reading from a socket Scheduling tasks to be executed on the event loop thread. The tradeoff, when enabling this feature, is that the event loop thread will be using 100% cpu, even when inactive. Modification: Added SelectStrategy option to return BUSY_WAIT Epoll loop will do a epoll_wait() with no timeout Use pause instruction to hint to processor that we're in a busy loop Result: When enabled, minimizes impact of context switch in the critical path
102 lines
3.7 KiB
Java
102 lines
3.7 KiB
Java
/*
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* Copyright 2018 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 java.util.ArrayList;
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import java.util.List;
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import org.junit.AfterClass;
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import org.junit.BeforeClass;
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import io.netty.bootstrap.Bootstrap;
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import io.netty.bootstrap.ServerBootstrap;
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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.SelectStrategyFactory;
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import io.netty.testsuite.transport.TestsuitePermutation;
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import io.netty.testsuite.transport.TestsuitePermutation.BootstrapComboFactory;
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import io.netty.testsuite.transport.TestsuitePermutation.BootstrapFactory;
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import io.netty.testsuite.transport.socket.SocketStringEchoTest;
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import io.netty.util.IntSupplier;
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import io.netty.util.concurrent.DefaultThreadFactory;
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public class EpollSocketStringEchoBusyWaitTest extends SocketStringEchoTest {
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private static EventLoopGroup EPOLL_LOOP;
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@BeforeClass
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public static void setup() throws Exception {
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EPOLL_LOOP = new EpollEventLoopGroup(2, new DefaultThreadFactory("testsuite-epoll-busy-wait", true),
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new SelectStrategyFactory() {
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@Override
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public SelectStrategy newSelectStrategy() {
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return new SelectStrategy() {
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@Override
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public int calculateStrategy(IntSupplier selectSupplier, boolean hasTasks) {
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return SelectStrategy.BUSY_WAIT;
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}
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};
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}
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});
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}
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@AfterClass
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public static void teardown() throws Exception {
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if (EPOLL_LOOP != null) {
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EPOLL_LOOP.shutdownGracefully();
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}
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}
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@Override
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protected List<TestsuitePermutation.BootstrapComboFactory<ServerBootstrap, Bootstrap>> newFactories() {
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List<BootstrapComboFactory<ServerBootstrap, Bootstrap>> list =
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new ArrayList<BootstrapComboFactory<ServerBootstrap, Bootstrap>>();
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final BootstrapFactory<ServerBootstrap> sbf = serverSocket();
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final BootstrapFactory<Bootstrap> cbf = clientSocket();
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list.add(new BootstrapComboFactory<ServerBootstrap, Bootstrap>() {
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@Override
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public ServerBootstrap newServerInstance() {
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return sbf.newInstance();
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}
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@Override
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public Bootstrap newClientInstance() {
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return cbf.newInstance();
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}
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});
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return list;
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}
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private static BootstrapFactory<ServerBootstrap> serverSocket() {
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return new BootstrapFactory<ServerBootstrap>() {
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@Override
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public ServerBootstrap newInstance() {
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return new ServerBootstrap().group(EPOLL_LOOP, EPOLL_LOOP).channel(EpollServerSocketChannel.class);
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}
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};
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}
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private static BootstrapFactory<Bootstrap> clientSocket() {
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return new BootstrapFactory<Bootstrap>() {
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@Override
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public Bootstrap newInstance() {
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return new Bootstrap().group(EPOLL_LOOP).channel(EpollSocketChannel.class);
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}
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};
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}
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}
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