Adding an execute burst cost benchmark for Netty executors (netty#8594)

Motivation:

Netty executors doesn't have yet any means to compare with each others
nor to compare with the j.u.c. executors

Modifications:

A new benchmark measuring execute burst cost is being added

Result:

It's now possible to compare some of Netty executors with each others
and with the j.u.c. executors

microbench/pom.xml

@@ -35,6 +35,9 @@
     <!-- This only be set when run on linux as on other platforms we just want to include the jar without native
          code -->
     <epoll.classifier />
+    <!-- This only be set when run on mac as on other platforms we just want to include the jar without native
+         code -->
+    <kqueue.classifier />
   </properties>
 
   <profiles>
@@ -61,6 +64,29 @@
         </plugins>
       </build>
     </profile>
+    <profile>
+      <id>mac</id>
+      <activation>
+        <os>
+          <family>mac</family>
+        </os>
+      </activation>
+      <properties>
+        <kqueue.classifier>${jni.classifier}</kqueue.classifier>
+      </properties>
+      <build>
+        <plugins>
+          <plugin>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <configuration>
+              <includes>
+                <include>**/*.java</include>
+              </includes>
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
     <profile>
       <id>benchmark-jar</id>
       <build>
@@ -132,6 +158,12 @@
       <version>${project.version}</version>
       <classifier>${epoll.classifier}</classifier>
     </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-transport-native-kqueue</artifactId>
+      <version>${project.version}</version>
+      <classifier>${kqueue.classifier}</classifier>
+    </dependency>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>

microbench/src/main/java/io/netty/microbench/concurrent/BurstCostExecutorsBenchmark.java

@@ -0,0 +1,331 @@
+/*
+ * Copyright 2018 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.microbench.concurrent;
+
+import io.netty.channel.epoll.Epoll;
+import io.netty.channel.epoll.EpollEventLoopGroup;
+import io.netty.channel.kqueue.KQueue;
+import io.netty.channel.kqueue.KQueueEventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.microbench.util.AbstractMicrobenchmark;
+import io.netty.util.concurrent.DefaultEventExecutor;
+import io.netty.util.internal.PlatformDependent;
+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.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.openjdk.jmh.annotations.Threads;
+import org.openjdk.jmh.infra.Blackhole;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Queue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
+
+@State(Scope.Benchmark)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+public class BurstCostExecutorsBenchmark extends AbstractMicrobenchmark {
+
+    /**
+     * This executor is useful as the best burst latency performer because it won't go to sleep and won't be hit by the
+     * cost of being awaken on both offer/consumer side.
+     */
+    private static final class SpinExecutorService implements ExecutorService {
+
+        private static final Runnable POISON_PILL = new Runnable() {
+            @Override
+            public void run() {
+            }
+        };
+        private final Queue<Runnable> tasks;
+        private final AtomicBoolean poisoned = new AtomicBoolean();
+        private final Thread executorThread;
+
+        public SpinExecutorService(int maxTasks) {
+            tasks = PlatformDependent.newFixedMpscQueue(maxTasks);
+            executorThread = new Thread(new Runnable() {
+                @Override
+                public void run() {
+                    final Queue<Runnable> tasks = SpinExecutorService.this.tasks;
+                    Runnable task;
+                    while ((task = tasks.poll()) != POISON_PILL) {
+                        if (task != null) {
+                            task.run();
+                        }
+                    }
+                }
+            });
+            executorThread.start();
+        }
+
+        @Override
+        public void shutdown() {
+            if (poisoned.compareAndSet(false, true)) {
+                while (!tasks.offer(POISON_PILL)) {
+                    // Just try again
+                }
+                try {
+                    executorThread.join();
+                } catch (InterruptedException e) {
+                    //We're quite trusty :)
+                }
+            }
+        }
+
+        @Override
+        public List<Runnable> shutdownNow() {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean isShutdown() {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean isTerminated() {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public <T> Future<T> submit(Callable<T> task) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public <T> Future<T> submit(Runnable task, T result) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public Future<?> submit(Runnable task) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) throws InterruptedException {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
+                throws InterruptedException {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
+                throws InterruptedException, ExecutionException {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public <T> T invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
+                throws InterruptedException, ExecutionException, TimeoutException {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public void execute(Runnable command) {
+            if (!tasks.offer(command)) {
+                throw new RejectedExecutionException(
+                        "If that happens, there is something wrong with the available capacity/burst size");
+            }
+        }
+    }
+
+    private enum ExecutorType {
+        spinning,
+        defaultEventExecutor,
+        juc,
+        nioEventLoop,
+        epollEventLoop,
+        kqueueEventLoop
+    }
+
+    @Param({ "1", "10" })
+    private int burstLength;
+    @Param({ "spinning", "epollEventLoop", "nioEventLoop", "defaultEventExecutor", "juc", "kqueueEventLoop" })
+    private String executorType;
+    @Param({ "0", "10" })
+    private int work;
+
+    private ExecutorService executor;
+    private ExecutorService executorToShutdown;
+
+    @Setup
+    public void setup() {
+        ExecutorType type = ExecutorType.valueOf(executorType);
+        switch (type) {
+        case spinning:
+            //The case with 3 producers can have a peak of 3*burstLength offers:
+            //4 is to leave some room between the offers and 1024 is to leave some room
+            //between producer/consumer when work is > 0 and 1 producer.
+            //If work = 0 then the task queue is supposed to be near empty most of the time.
+            executor = new SpinExecutorService(Math.min(1024, burstLength * 4));
+            executorToShutdown = executor;
+            break;
+        case defaultEventExecutor:
+            executor = new DefaultEventExecutor();
+            executorToShutdown = executor;
+            break;
+        case juc:
+            executor = Executors.newSingleThreadScheduledExecutor();
+            executorToShutdown = executor;
+            break;
+        case nioEventLoop:
+            NioEventLoopGroup nioEventLoopGroup = new NioEventLoopGroup(1);
+            nioEventLoopGroup.setIoRatio(1);
+            executor = nioEventLoopGroup.next();
+            executorToShutdown = nioEventLoopGroup;
+            break;
+        case epollEventLoop:
+            Epoll.ensureAvailability();
+            EpollEventLoopGroup epollEventLoopGroup = new EpollEventLoopGroup(1);
+            epollEventLoopGroup.setIoRatio(1);
+            executor = epollEventLoopGroup.next();
+            executorToShutdown = epollEventLoopGroup;
+            break;
+        case kqueueEventLoop:
+            KQueue.ensureAvailability();
+            KQueueEventLoopGroup kQueueEventLoopGroup = new KQueueEventLoopGroup(1);
+            kQueueEventLoopGroup.setIoRatio(1);
+            executor = kQueueEventLoopGroup.next();
+            executorToShutdown = kQueueEventLoopGroup;
+            break;
+        }
+    }
+
+    @TearDown
+    public void tearDown() {
+        executorToShutdown.shutdown();
+    }
+
+    @State(Scope.Thread)
+    public static class PerThreadState {
+        //To reduce the benchmark noise we avoid using AtomicInteger that would
+        //suffer of false sharing while reading/writing the counter due to the surrounding
+        //instances on heap: thanks to JMH the "completed" field will be padded
+        //avoiding false-sharing for free
+        private static final AtomicIntegerFieldUpdater<PerThreadState> DONE_UPDATER =
+                AtomicIntegerFieldUpdater.newUpdater(PerThreadState.class, "completed");
+        private volatile int completed;
+
+        private Runnable completeTask;
+
+        @Setup
+        public void setup(BurstCostExecutorsBenchmark bench) {
+            final int work = bench.work;
+            if (work > 0) {
+                completeTask = new Runnable() {
+                    @Override
+                    public void run() {
+                        Blackhole.consumeCPU(work);
+                        //We can avoid the full barrier cost of a volatile set given that the
+                        //benchmark is focusing on executors with a single threaded consumer:
+                        //it would reduce the cost on consumer side while allowing to focus just
+                        //to the threads hand-off/wake-up cost
+                        DONE_UPDATER.lazySet(PerThreadState.this, completed + 1);
+                    }
+                };
+            } else {
+                completeTask = new Runnable() {
+                    @Override
+                    public void run() {
+                        //We can avoid the full barrier cost of a volatile set given that the
+                        //benchmark is focusing on executors with a single threaded consumer:
+                        //it would reduce the cost on consumer side while allowing to focus just
+                        //to the threads hand-off/wake-up cost
+                        DONE_UPDATER.lazySet(PerThreadState.this, completed + 1);
+                    }
+                };
+            }
+        }
+
+        /**
+         * Single-writer reset of completed counter.
+         */
+        public void resetCompleted() {
+            //We can avoid the full barrier cost of a volatile set given that
+            //the counter can be reset from a single thread and it should be reset
+            //only after any submitted tasks are completed
+            DONE_UPDATER.lazySet(this, 0);
+        }
+
+        /**
+         * It would spin-wait until at least {@code value} tasks are being completed.
+         */
+        public int spinWaitCompletionOf(int value) {
+            while (true) {
+                final int lastRead = this.completed;
+                if (lastRead >= value) {
+                    return lastRead;
+                }
+            }
+        }
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.SampleTime)
+    @Threads(1)
+    public int test1Producer(final PerThreadState state) {
+        return executeBurst(state);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.SampleTime)
+    @Threads(2)
+    public int test2Producers(final PerThreadState state) {
+        return executeBurst(state);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.SampleTime)
+    @Threads(3)
+    public int test3Producers(final PerThreadState state) {
+        return executeBurst(state);
+    }
+
+    private int executeBurst(final PerThreadState state) {
+        final ExecutorService executor = this.executor;
+        final int burstLength = this.burstLength;
+        final Runnable completeTask = state.completeTask;
+        for (int i = 0; i < burstLength; i++) {
+            executor.execute(completeTask);
+        }
+        final int value = state.spinWaitCompletionOf(burstLength);
+        state.resetCompleted();
+        return value;
+    }
+}