Speed up the slow path of FastThreadLocal

Motivation:

The current slow path of FastThreadLocal is much slower than JDK ThreadLocal. See #4418

Modifications:

- Add FastThreadLocalSlowPathBenchmark for the flow path of FastThreadLocal
- Add final to speed up the slow path of FastThreadLocal

Result:

The slow path of FastThreadLocal is improved.

common/src/main/java/io/netty/util/internal/InternalThreadLocalMap.java

@@ -38,18 +38,10 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
 
     public static InternalThreadLocalMap getIfSet() {
         Thread thread = Thread.currentThread();
-        InternalThreadLocalMap threadLocalMap;
         if (thread instanceof FastThreadLocalThread) {
-            threadLocalMap = ((FastThreadLocalThread) thread).threadLocalMap();
+            return ((FastThreadLocalThread) thread).threadLocalMap();
-        } else {
-            ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = UnpaddedInternalThreadLocalMap.slowThreadLocalMap;
-            if (slowThreadLocalMap == null) {
-                threadLocalMap = null;
-            } else {
-                threadLocalMap = slowThreadLocalMap.get();
-            }
         }
-        return threadLocalMap;
+        return slowThreadLocalMap.get();
     }
 
     public static InternalThreadLocalMap get() {
@@ -71,11 +63,6 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
 
     private static InternalThreadLocalMap slowGet() {
         ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = UnpaddedInternalThreadLocalMap.slowThreadLocalMap;
-        if (slowThreadLocalMap == null) {
-            UnpaddedInternalThreadLocalMap.slowThreadLocalMap =
-                    slowThreadLocalMap = new ThreadLocal<InternalThreadLocalMap>();
-        }
-
         InternalThreadLocalMap ret = slowThreadLocalMap.get();
         if (ret == null) {
             ret = new InternalThreadLocalMap();
@@ -89,15 +76,12 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
         if (thread instanceof FastThreadLocalThread) {
             ((FastThreadLocalThread) thread).setThreadLocalMap(null);
         } else {
-            ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = UnpaddedInternalThreadLocalMap.slowThreadLocalMap;
+            slowThreadLocalMap.remove();
-            if (slowThreadLocalMap != null) {
-                slowThreadLocalMap.remove();
-            }
         }
     }
 
     public static void destroy() {
-        slowThreadLocalMap = null;
+        slowThreadLocalMap.remove();
     }
 
     public static int nextVariableIndex() {

common/src/main/java/io/netty/util/internal/UnpaddedInternalThreadLocalMap.java

@@ -31,7 +31,7 @@ import java.util.concurrent.atomic.AtomicInteger;
  */
 class UnpaddedInternalThreadLocalMap {
 
-    static ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap;
+    static final ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = new ThreadLocal<InternalThreadLocalMap>();
     static final AtomicInteger nextIndex = new AtomicInteger();
 
     /** Used by {@link FastThreadLocal} */

microbench/src/test/java/io/netty/microbench/concurrent/FastThreadLocalFastPathBenchmark.java

@@ -24,11 +24,11 @@ import org.openjdk.jmh.annotations.Threads;
 import java.util.Random;
 
 /**
- * This class benchmarks different allocators with different allocation sizes.
+ * This class benchmarks the fast path of FastThreadLocal and the JDK ThreadLocal.
  */
 @Threads(4)
 @Measurement(iterations = 10, batchSize = 100)
-public class FastThreadLocalBenchmark extends AbstractMicrobenchmark {
+public class FastThreadLocalFastPathBenchmark extends AbstractMicrobenchmark {
 
     private static final Random rand = new Random();
 
@@ -39,19 +39,17 @@ public class FastThreadLocalBenchmark extends AbstractMicrobenchmark {
 
     static {
         for (int i = 0; i < jdkThreadLocals.length; i ++) {
+            final int num = rand.nextInt();
             jdkThreadLocals[i] = new ThreadLocal<Integer>() {
                 @Override
                 protected Integer initialValue() {
-                    return rand.nextInt();
+                    return num;
                 }
             };
-        }
-
-        for (int i = 0; i < fastThreadLocals.length; i ++) {
             fastThreadLocals[i] = new FastThreadLocal<Integer>() {
                 @Override
                 protected Integer initialValue() {
-                    return rand.nextInt();
+                    return num;
                 }
             };
         }

microbench/src/test/java/io/netty/microbench/concurrent/FastThreadLocalSlowPathBenchmark.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2016 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.microbench.util.AbstractMicrobenchmark;
+import io.netty.util.concurrent.FastThreadLocal;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Threads;
+
+import java.util.Random;
+
+/**
+ * This class benchmarks the slow path of FastThreadLocal and the JDK ThreadLocal.
+ */
+@Threads(4)
+@Measurement(iterations = 10, batchSize = 100)
+public class FastThreadLocalSlowPathBenchmark extends AbstractMicrobenchmark {
+
+    private static final Random rand = new Random();
+
+    @SuppressWarnings("unchecked")
+    private static final ThreadLocal<Integer>[] jdkThreadLocals = new ThreadLocal[128];
+    @SuppressWarnings("unchecked")
+    private static final FastThreadLocal<Integer>[] fastThreadLocals = new FastThreadLocal[jdkThreadLocals.length];
+
+    static {
+        for (int i = 0; i < jdkThreadLocals.length; i ++) {
+            final int num = rand.nextInt();
+            jdkThreadLocals[i] = new ThreadLocal<Integer>() {
+                @Override
+                protected Integer initialValue() {
+                    return num;
+                }
+            };
+            fastThreadLocals[i] = new FastThreadLocal<Integer>() {
+                @Override
+                protected Integer initialValue() {
+                    return num;
+                }
+            };
+        }
+    }
+
+    public FastThreadLocalSlowPathBenchmark() {
+        super(false, true);
+    }
+
+    @Benchmark
+    public int jdkThreadLocalGet() {
+        int result = 0;
+        for (ThreadLocal<Integer> i: jdkThreadLocals) {
+            result += i.get();
+        }
+        return result;
+    }
+
+    @Benchmark
+    public int fastThreadLocal() {
+        int result = 0;
+        for (FastThreadLocal<Integer> i: fastThreadLocals) {
+            result += i.get();
+        }
+        return result;
+    }
+}

microbench/src/test/java/io/netty/microbench/util/AbstractMicrobenchmark.java

@@ -15,36 +15,22 @@
  */
 package io.netty.microbench.util;
 
-import io.netty.util.ResourceLeakDetector;
 import io.netty.util.concurrent.DefaultThreadFactory;
 import io.netty.util.internal.SystemPropertyUtil;
-import org.junit.Test;
-import org.openjdk.jmh.annotations.Fork;
-import org.openjdk.jmh.annotations.Measurement;
-import org.openjdk.jmh.annotations.Scope;
-import org.openjdk.jmh.annotations.State;
-import org.openjdk.jmh.annotations.Warmup;
-import org.openjdk.jmh.results.format.ResultFormatType;
-import org.openjdk.jmh.runner.Runner;
-import org.openjdk.jmh.runner.options.ChainedOptionsBuilder;
-import org.openjdk.jmh.runner.options.OptionsBuilder;
 
-import java.io.File;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
-/**
+import org.openjdk.jmh.annotations.Fork;
- * Base class for all JMH benchmarks.
+import org.openjdk.jmh.runner.options.ChainedOptionsBuilder;
- */
+
-@Warmup(iterations = AbstractMicrobenchmark.DEFAULT_WARMUP_ITERATIONS)
+/**
-@Measurement(iterations = AbstractMicrobenchmark.DEFAULT_MEASURE_ITERATIONS)
+ * Default implementation of the JMH microbenchmark adapter.  There may be context switches introduced by this harness.
-@Fork(AbstractMicrobenchmark.DEFAULT_FORKS)
+ */
-@State(Scope.Thread)
+@Fork(AbstractMicrobenchmark.DEFAULT_FORKS)
-public class AbstractMicrobenchmark {
+public class AbstractMicrobenchmark extends AbstractMicrobenchmarkBase {
 
-    protected static final int DEFAULT_WARMUP_ITERATIONS = 10;
-    protected static final int DEFAULT_MEASURE_ITERATIONS = 10;
     protected static final int DEFAULT_FORKS = 2;
 
     public static final class HarnessExecutor extends ThreadPoolExecutor {
@@ -55,69 +41,49 @@ public class AbstractMicrobenchmark {
         }
     }
 
-    protected static final String[] JVM_ARGS = {
+    private final String[] jvmArgs;
-        "-server", "-dsa", "-da", "-ea:io.netty...", "-Xms768m", "-Xmx768m",
-        "-XX:MaxDirectMemorySize=768m", "-XX:+AggressiveOpts", "-XX:+UseBiasedLocking",
-        "-XX:+UseFastAccessorMethods", "-XX:+UseStringCache", "-XX:+OptimizeStringConcat",
-        "-XX:+HeapDumpOnOutOfMemoryError", "-Dio.netty.noResourceLeakDetection",
-        "-Djmh.executor=CUSTOM",
-        "-Djmh.executor.class=io.netty.microbench.util.AbstractMicrobenchmark$HarnessExecutor"
-    };
 
-    static {
+    public AbstractMicrobenchmark() {
-        ResourceLeakDetector.setLevel(ResourceLeakDetector.Level.DISABLED);
+        this(false, false);
     }
 
-    @Test
+    public AbstractMicrobenchmark(boolean disableAssertions) {
-    public void run() throws Exception {
+        this(disableAssertions, false);
-        String className = getClass().getSimpleName();
+    }
 
-        ChainedOptionsBuilder runnerOptions = new OptionsBuilder()
+    public AbstractMicrobenchmark(boolean disableAssertions, boolean disableHarnessExecutor) {
-            .include(".*" + className + ".*")
+        final String[] customArgs;
-            .jvmArgs(JVM_ARGS);
+        if (disableHarnessExecutor) {
-
+            customArgs = new String[]{"-Xms768m", "-Xmx768m", "-XX:MaxDirectMemorySize=768m"};
-        if (getWarmupIterations() > 0) {
+        } else {
-            runnerOptions.warmupIterations(getWarmupIterations());
+            customArgs = new String[]{"-Xms768m", "-Xmx768m", "-XX:MaxDirectMemorySize=768m", "-Djmh.executor=CUSTOM",
+                    "-Djmh.executor.class=io.netty.microbench.util.AbstractMicrobenchmark$HarnessExecutor"};
         }
-
+        String[] jvmArgs = new String[BASE_JVM_ARGS.length + customArgs.length];
-        if (getMeasureIterations() > 0) {
+        System.arraycopy(BASE_JVM_ARGS, 0, jvmArgs, 0, BASE_JVM_ARGS.length);
-            runnerOptions.measurementIterations(getMeasureIterations());
+        System.arraycopy(customArgs, 0, jvmArgs, BASE_JVM_ARGS.length, customArgs.length);
+        if (disableAssertions) {
+            jvmArgs = removeAssertions(jvmArgs);
         }
+        this.jvmArgs = jvmArgs;
+    }
 
+    @Override
+    protected String[] jvmArgs() {
+        return jvmArgs;
+    }
+
+    @Override
+    protected ChainedOptionsBuilder newOptionsBuilder() throws Exception {
+        ChainedOptionsBuilder runnerOptions = super.newOptionsBuilder();
         if (getForks() > 0) {
             runnerOptions.forks(getForks());
         }
 
-        if (getReportDir() != null) {
+        return runnerOptions;
-            String filePath = getReportDir() + className + ".json";
-            File file = new File(filePath);
-            if (file.exists()) {
-                file.delete();
-            } else {
-                file.getParentFile().mkdirs();
-                file.createNewFile();
-            }
-
-            runnerOptions.resultFormat(ResultFormatType.JSON);
-            runnerOptions.result(filePath);
-        }
-
-        new Runner(runnerOptions.build()).run();
-    }
-
-    protected int getWarmupIterations() {
-        return SystemPropertyUtil.getInt("warmupIterations", -1);
-    }
-
-    protected int getMeasureIterations() {
-        return SystemPropertyUtil.getInt("measureIterations", -1);
     }
 
     protected int getForks() {
         return SystemPropertyUtil.getInt("forks", -1);
     }
-
-    protected String getReportDir() {
-        return SystemPropertyUtil.get("perfReportDir");
-    }
 }

microbench/src/test/java/io/netty/microbench/util/AbstractMicrobenchmarkBase.java

@@ -0,0 +1,122 @@
+/*
+ * 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.microbench.util;
+
+import static org.junit.Assert.assertNull;
+import io.netty.util.ResourceLeakDetector;
+import io.netty.util.internal.SystemPropertyUtil;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.results.format.ResultFormatType;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.ChainedOptionsBuilder;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+/**
+ * Base class for all JMH benchmarks.
+ */
+@Warmup(iterations = AbstractMicrobenchmarkBase.DEFAULT_WARMUP_ITERATIONS)
+@Measurement(iterations = AbstractMicrobenchmarkBase.DEFAULT_MEASURE_ITERATIONS)
+@State(Scope.Thread)
+public abstract class AbstractMicrobenchmarkBase {
+    protected static final int DEFAULT_WARMUP_ITERATIONS = 10;
+    protected static final int DEFAULT_MEASURE_ITERATIONS = 10;
+    protected static final String[] BASE_JVM_ARGS = {
+            "-server", "-dsa", "-da", "-ea:io.netty...", "-XX:+AggressiveOpts", "-XX:+UseBiasedLocking",
+            "-XX:+UseFastAccessorMethods", "-XX:+OptimizeStringConcat",
+            "-XX:+HeapDumpOnOutOfMemoryError", "-Dio.netty.noResourceLeakDetection"};
+
+    static {
+        ResourceLeakDetector.setLevel(ResourceLeakDetector.Level.DISABLED);
+    }
+
+    protected ChainedOptionsBuilder newOptionsBuilder() throws Exception {
+        String className = getClass().getSimpleName();
+
+        ChainedOptionsBuilder runnerOptions = new OptionsBuilder()
+                .include(".*" + className + ".*")
+                .jvmArgs(jvmArgs());
+
+        if (getWarmupIterations() > 0) {
+            runnerOptions.warmupIterations(getWarmupIterations());
+        }
+
+        if (getMeasureIterations() > 0) {
+            runnerOptions.measurementIterations(getMeasureIterations());
+        }
+
+        if (getReportDir() != null) {
+            String filePath = getReportDir() + className + ".json";
+            File file = new File(filePath);
+            if (file.exists()) {
+                file.delete();
+            } else {
+                file.getParentFile().mkdirs();
+                file.createNewFile();
+            }
+
+            runnerOptions.resultFormat(ResultFormatType.JSON);
+            runnerOptions.result(filePath);
+        }
+
+        return runnerOptions;
+    }
+
+    protected abstract String[] jvmArgs();
+
+    protected static String[] removeAssertions(String[] jvmArgs) {
+        List<String> customArgs = new ArrayList<String>(jvmArgs.length);
+        for (String arg : jvmArgs) {
+            if (!arg.startsWith("-ea")) {
+                customArgs.add(arg);
+            }
+        }
+        if (jvmArgs.length != customArgs.size()) {
+            jvmArgs = new String[customArgs.size()];
+            customArgs.toArray(jvmArgs);
+        }
+        return jvmArgs;
+    }
+
+    @Test
+    public void run() throws Exception {
+        new Runner(newOptionsBuilder().build()).run();
+    }
+
+    protected int getWarmupIterations() {
+        return SystemPropertyUtil.getInt("warmupIterations", -1);
+    }
+
+    protected int getMeasureIterations() {
+        return SystemPropertyUtil.getInt("measureIterations", -1);
+    }
+
+    protected String getReportDir() {
+        return SystemPropertyUtil.get("perfReportDir");
+    }
+
+    public static void handleUnexpectedException(Throwable t) {
+        assertNull(t);
+    }
+}