Refactor FastThreadLocal to simplify TLV management

Motivation:

When Netty runs in a managed environment such as web application server,
Netty needs to provide an explicit way to remove the thread-local
variables it created to prevent class loader leaks.

FastThreadLocal uses different execution paths for storing a
thread-local variable depending on the type of the current thread.
It increases the complexity of thread-local removal.

Modifications:

- Moved FastThreadLocal and FastThreadLocalThread out of the internal
  package so that a user can use it.
- FastThreadLocal now keeps track of all thread local variables it has
  initialized, and calling FastThreadLocal.removeAll() will remove all
  thread-local variables of the caller thread.
- Added FastThreadLocal.size() for diagnostics and tests
- Introduce InternalThreadLocalMap which is a mixture of hard-wired
  thread local variable fields and extensible indexed variables
- FastThreadLocal now uses InternalThreadLocalMap to implement a
  thread-local variable.
- Added ThreadDeathWatcher.unwatch() so that PooledByteBufAllocator
  tells it to stop watching when its thread-local cache has been freed
  by FastThreadLocal.removeAll().
- Added FastThreadLocalTest to ensure that removeAll() works
- Added microbenchmark for FastThreadLocal and JDK ThreadLocal
- Upgraded to JMH 0.9

Result:

- A user can remove all thread-local variables Netty created, as long as
  he or she did not exit from the current thread. (Note that there's no
  way to remove a thread-local variable from outside of the thread.)
- FastThreadLocal exposes more useful operations such as isSet() because
  we always implement a thread local variable via InternalThreadLocalMap
  instead of falling back to JDK ThreadLocal.
- FastThreadLocalBenchmark shows that this change improves the
  performance of FastThreadLocal even more.

buffer/src/main/java/io/netty/buffer/PoolThreadCache.java

@@ -17,6 +17,10 @@
 package io.netty.buffer;
 
 
+import io.netty.util.ThreadDeathWatcher;
+import io.netty.util.internal.logging.InternalLogger;
+import io.netty.util.internal.logging.InternalLoggerFactory;
+
 import java.nio.ByteBuffer;
 
 /**
@@ -26,6 +30,9 @@ import java.nio.ByteBuffer;
  * 480222803919">Scalable memory allocation using jemalloc</a>.
  */
 final class PoolThreadCache {
+
+    private static final InternalLogger logger = InternalLoggerFactory.getInstance(PoolThreadCache.class);
+
     final PoolArena<byte[]> heapArena;
     final PoolArena<ByteBuffer> directArena;
 
@@ -44,6 +51,14 @@ final class PoolThreadCache {
 
     private int allocations;
 
+    private final Thread thread = Thread.currentThread();
+    private final Runnable freeTask = new Runnable() {
+        @Override
+        public void run() {
+            free0();
+        }
+    };
+
     // TODO: Test if adding padding helps under contention
     //private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
 
@@ -90,6 +105,10 @@ final class PoolThreadCache {
             normalHeapCaches = null;
             numShiftsNormalHeap = -1;
         }
+
+        // The thread-local cache will keep a list of pooled buffers which must be returned to
+        // the pool when the thread is not alive anymore.
+        ThreadDeathWatcher.watch(thread, freeTask);
     }
 
     private static <T> SubPageMemoryRegionCache<T>[] createSubPageCaches(int cacheSize, int numCaches) {
@@ -192,13 +211,22 @@ final class PoolThreadCache {
     /**
      *  Should be called if the Thread that uses this cache is about to exist to release resources out of the cache
      */
-    int free() {
-        return free(tinySubPageDirectCaches) +
+    void free() {
+        ThreadDeathWatcher.unwatch(thread, freeTask);
+        free0();
+    }
+
+    private void free0() {
+        int numFreed = free(tinySubPageDirectCaches) +
                 free(smallSubPageDirectCaches) +
                 free(normalDirectCaches) +
                 free(tinySubPageHeapCaches) +
                 free(smallSubPageHeapCaches) +
                 free(normalHeapCaches);
+
+        if (numFreed > 0 && logger.isDebugEnabled()) {
+            logger.debug("Freed {} thread-local buffer(s) from thread: {}", numFreed, thread.getName());
+        }
     }
 
     private static int free(MemoryRegionCache<?>[] caches) {

buffer/src/main/java/io/netty/buffer/PooledByteBufAllocator.java

@@ -16,8 +16,7 @@
 
 package io.netty.buffer;
 
-import io.netty.util.ThreadDeathWatcher;
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocal;
 import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.SystemPropertyUtil;
 import io.netty.util.internal.logging.InternalLogger;
@@ -277,24 +276,14 @@ public class PooledByteBufAllocator extends AbstractByteBufAllocator {
                 directArena = null;
             }
 
-            final PoolThreadCache cache = new PoolThreadCache(
+            return new PoolThreadCache(
                     heapArena, directArena, tinyCacheSize, smallCacheSize, normalCacheSize,
                     DEFAULT_MAX_CACHED_BUFFER_CAPACITY, DEFAULT_CACHE_TRIM_INTERVAL);
+        }
 
-            // The thread-local cache will keep a list of pooled buffers which must be returned to
-            // the pool when the thread is not alive anymore.
-            final Thread thread = Thread.currentThread();
-            ThreadDeathWatcher.watch(thread, new Runnable() {
-                @Override
-                public void run() {
-                    int numFreed = cache.free();
-                    if (logger.isDebugEnabled()) {
-                        logger.debug("Freed {} thread-local buffer(s) from thread: {}", numFreed, thread.getName());
-                    }
-                }
-            });
-
-            return cache;
+        @Override
+        protected void onRemoval(PoolThreadCache value) {
+            value.free();
         }
     }
 

codec-http/src/main/java/io/netty/handler/codec/http/ClientCookieEncoder.java

@@ -42,7 +42,7 @@ public final class ClientCookieEncoder {
             throw new NullPointerException("cookie");
         }
 
-        StringBuilder buf = buffer.get();
+        StringBuilder buf = stringBuilder();
         encode(buf, cookie);
         return stripTrailingSeparator(buf);
     }
@@ -52,7 +52,7 @@ public final class ClientCookieEncoder {
             throw new NullPointerException("cookies");
         }
 
-        StringBuilder buf = buffer.get();
+        StringBuilder buf = stringBuilder();
         for (Cookie c: cookies) {
             if (c == null) {
                 break;
@@ -68,7 +68,7 @@ public final class ClientCookieEncoder {
             throw new NullPointerException("cookies");
         }
 
-        StringBuilder buf = buffer.get();
+        StringBuilder buf = stringBuilder();
         for (Cookie c: cookies) {
             if (c == null) {
                 break;

codec-http/src/main/java/io/netty/handler/codec/http/CookieEncoderUtil.java

@@ -16,23 +16,13 @@
 package io.netty.handler.codec.http;
 
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.internal.InternalThreadLocalMap;
 
 final class CookieEncoderUtil {
 
-    static final ThreadLocal<StringBuilder> buffer = new FastThreadLocal<StringBuilder>() {
-        @Override
-        public StringBuilder get() {
-            StringBuilder buf = super.get();
-            buf.setLength(0);
-            return buf;
-        }
-
-        @Override
-        protected StringBuilder initialValue() {
-            return new StringBuilder(512);
-        }
-    };
+    static StringBuilder stringBuilder() {
+        return InternalThreadLocalMap.get().stringBuilder();
+    }
 
     static String stripTrailingSeparator(StringBuilder buf) {
         if (buf.length() > 0) {

codec-http/src/main/java/io/netty/handler/codec/http/HttpHeaderDateFormat.java

@@ -15,7 +15,7 @@
  */
 package io.netty.handler.codec.http;
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocal;
 
 import java.text.ParsePosition;
 import java.text.SimpleDateFormat;
@@ -39,7 +39,7 @@ final class HttpHeaderDateFormat extends SimpleDateFormat {
     private final SimpleDateFormat format1 = new HttpHeaderDateFormatObsolete1();
     private final SimpleDateFormat format2 = new HttpHeaderDateFormatObsolete2();
 
-    private static final ThreadLocal<HttpHeaderDateFormat> dateFormatThreadLocal =
+    private static final FastThreadLocal<HttpHeaderDateFormat> dateFormatThreadLocal =
             new FastThreadLocal<HttpHeaderDateFormat>() {
                 @Override
                 protected HttpHeaderDateFormat initialValue() {

codec-http/src/main/java/io/netty/handler/codec/http/ServerCookieEncoder.java

@@ -47,7 +47,7 @@ public final class ServerCookieEncoder {
             throw new NullPointerException("cookie");
         }
 
-        StringBuilder buf = buffer.get();
+        StringBuilder buf = stringBuilder();
 
         add(buf, cookie.getName(), cookie.getValue());
 

codec/src/main/java/io/netty/handler/codec/DefaultTextHeaders.java

@@ -16,7 +16,7 @@
 
 package io.netty.handler.codec;
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocal;
 import io.netty.util.internal.PlatformDependent;
 
 import java.text.DateFormat;
@@ -769,7 +769,7 @@ public class DefaultTextHeaders implements TextHeaders {
     static final class HttpHeaderDateFormat {
 
         private static final ParsePosition parsePos = new ParsePosition(0);
-        private static final ThreadLocal<HttpHeaderDateFormat> dateFormatThreadLocal =
+        private static final FastThreadLocal<HttpHeaderDateFormat> dateFormatThreadLocal =
                 new FastThreadLocal<HttpHeaderDateFormat>() {
                     @Override
                     protected HttpHeaderDateFormat initialValue() {

codec/src/main/java/io/netty/handler/codec/marshalling/ThreadLocalMarshallerProvider.java

@@ -17,7 +17,7 @@ package io.netty.handler.codec.marshalling;
 
 import io.netty.channel.ChannelHandlerContext;
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocal;
 import org.jboss.marshalling.Marshaller;
 import org.jboss.marshalling.MarshallerFactory;
 import org.jboss.marshalling.MarshallingConfiguration;
@@ -28,7 +28,7 @@ import org.jboss.marshalling.MarshallingConfiguration;
  * many small {@link Object}'s and your actual Thread count is not to big
  */
 public class ThreadLocalMarshallerProvider implements MarshallerProvider {
-    private final ThreadLocal<Marshaller> marshallers = new FastThreadLocal<Marshaller>();
+    private final FastThreadLocal<Marshaller> marshallers = new FastThreadLocal<Marshaller>();
 
     private final MarshallerFactory factory;
     private final MarshallingConfiguration config;

codec/src/main/java/io/netty/handler/codec/marshalling/ThreadLocalUnmarshallerProvider.java

@@ -17,7 +17,7 @@ package io.netty.handler.codec.marshalling;
 
 import io.netty.channel.ChannelHandlerContext;
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocal;
 import org.jboss.marshalling.MarshallerFactory;
 import org.jboss.marshalling.MarshallingConfiguration;
 import org.jboss.marshalling.Unmarshaller;
@@ -28,7 +28,7 @@ import org.jboss.marshalling.Unmarshaller;
  * many small {@link Object}'s.
  */
 public class ThreadLocalUnmarshallerProvider implements UnmarshallerProvider {
-    private final ThreadLocal<Unmarshaller> unmarshallers = new FastThreadLocal<Unmarshaller>();
+    private final FastThreadLocal<Unmarshaller> unmarshallers = new FastThreadLocal<Unmarshaller>();
 
     private final MarshallerFactory factory;
     private final MarshallingConfiguration config;

common/src/main/java/io/netty/util/CharsetUtil.java

@@ -15,13 +15,12 @@
  */
 package io.netty.util;
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.internal.InternalThreadLocalMap;
 
 import java.nio.charset.Charset;
 import java.nio.charset.CharsetDecoder;
 import java.nio.charset.CharsetEncoder;
 import java.nio.charset.CodingErrorAction;
-import java.util.IdentityHashMap;
 import java.util.Map;
 
 /**
@@ -62,22 +61,6 @@ public final class CharsetUtil {
      */
     public static final Charset US_ASCII = Charset.forName("US-ASCII");
 
-    private static final ThreadLocal<Map<Charset, CharsetEncoder>> encoders =
-        new FastThreadLocal<Map<Charset, CharsetEncoder>>() {
-            @Override
-            protected Map<Charset, CharsetEncoder> initialValue() {
-                return new IdentityHashMap<Charset, CharsetEncoder>();
-            }
-        };
-
-    private static final ThreadLocal<Map<Charset, CharsetDecoder>> decoders =
-        new FastThreadLocal<Map<Charset, CharsetDecoder>>() {
-            @Override
-            protected Map<Charset, CharsetDecoder> initialValue() {
-                return new IdentityHashMap<Charset, CharsetDecoder>();
-            }
-        };
-
     /**
      * Returns a cached thread-local {@link CharsetEncoder} for the specified
      * <tt>charset</tt>.
@@ -87,7 +70,7 @@ public final class CharsetUtil {
             throw new NullPointerException("charset");
         }
 
-        Map<Charset, CharsetEncoder> map = encoders.get();
+        Map<Charset, CharsetEncoder> map = InternalThreadLocalMap.get().charsetEncoderCache();
         CharsetEncoder e = map.get(charset);
         if (e != null) {
             e.reset();
@@ -112,7 +95,7 @@ public final class CharsetUtil {
             throw new NullPointerException("charset");
         }
 
-        Map<Charset, CharsetDecoder> map = decoders.get();
+        Map<Charset, CharsetDecoder> map = InternalThreadLocalMap.get().charsetDecoderCache();
         CharsetDecoder d = map.get(charset);
         if (d != null) {
             d.reset();

common/src/main/java/io/netty/util/Recycler.java

@@ -16,6 +16,7 @@
 
 package io.netty.util;
 
+import io.netty.util.concurrent.FastThreadLocal;
 import io.netty.util.internal.SystemPropertyUtil;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
@@ -23,8 +24,6 @@ import io.netty.util.internal.logging.InternalLoggerFactory;
 import java.util.IdentityHashMap;
 import java.util.Map;
 
-import io.netty.util.internal.FastThreadLocal;
-
 /**
  * Light-weight object pool based on a thread-local stack.
  *
@@ -56,7 +55,7 @@ public abstract class Recycler<T> {
     }
 
     private final int maxCapacity;
-    private final ThreadLocal<Stack<T>> threadLocal = new FastThreadLocal<Stack<T>>() {
+    private final FastThreadLocal<Stack<T>> threadLocal = new FastThreadLocal<Stack<T>>() {
         @Override
         protected Stack<T> initialValue() {
             return new Stack<T>(Recycler.this, Thread.currentThread(), maxCapacity);
@@ -67,7 +66,7 @@ public abstract class Recycler<T> {
         this(DEFAULT_MAX_CAPACITY);
     }
 
-    public Recycler(int maxCapacity) {
+    protected Recycler(int maxCapacity) {
         this.maxCapacity = Math.max(0, maxCapacity);
     }
 

common/src/main/java/io/netty/util/ThreadDeathWatcher.java

@@ -67,7 +67,25 @@ public final class ThreadDeathWatcher {
             throw new IllegalArgumentException("thread must be alive.");
         }
 
-        pendingEntries.add(new Entry(thread, task));
+        schedule(thread, task, true);
+    }
+
+    /**
+     * Cancels the task scheduled via {@link #watch(Thread, Runnable)}.
+     */
+    public static void unwatch(Thread thread, Runnable task) {
+        if (thread == null) {
+            throw new NullPointerException("thread");
+        }
+        if (task == null) {
+            throw new NullPointerException("task");
+        }
+
+        schedule(thread, task, false);
+    }
+
+    private static void schedule(Thread thread, Runnable task, boolean isWatch) {
+        pendingEntries.add(new Entry(thread, task, isWatch));
 
         if (started.compareAndSet(false, true)) {
             Thread watcherThread = threadFactory.newThread(watcher);
@@ -93,8 +111,10 @@ public final class ThreadDeathWatcher {
         Thread watcherThread = ThreadDeathWatcher.watcherThread;
         if (watcherThread != null) {
             watcherThread.join(unit.toMillis(timeout));
+            return !watcherThread.isAlive();
+        } else {
+            return true;
         }
-        return !watcherThread.isAlive();
     }
 
     private ThreadDeathWatcher() { }
@@ -109,6 +129,10 @@ public final class ThreadDeathWatcher {
                 fetchWatchees();
                 notifyWatchees();
 
+                // Try once again just in case notifyWatchees() triggered watch() or unwatch().
+                fetchWatchees();
+                notifyWatchees();
+
                 try {
                     Thread.sleep(1000);
                 } catch (InterruptedException ignore) {
@@ -153,7 +177,11 @@ public final class ThreadDeathWatcher {
                     break;
                 }
 
-                watchees.add(e);
+                if (e.isWatch) {
+                    watchees.add(e);
+                } else {
+                    watchees.remove(e);
+                }
             }
         }
 
@@ -178,15 +206,36 @@ public final class ThreadDeathWatcher {
     private static final class Entry extends MpscLinkedQueueNode<Entry> {
         final Thread thread;
         final Runnable task;
+        final boolean isWatch;
 
-        Entry(Thread thread, Runnable task) {
+        Entry(Thread thread, Runnable task, boolean isWatch) {
             this.thread = thread;
             this.task = task;
+            this.isWatch = isWatch;
         }
 
         @Override
         public Entry value() {
             return this;
         }
+
+        @Override
+        public int hashCode() {
+            return thread.hashCode() ^ task.hashCode();
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (obj == this) {
+                return true;
+            }
+
+            if (!(obj instanceof Entry)) {
+                return false;
+            }
+
+            Entry that = (Entry) obj;
+            return thread == that.thread && task == that.task;
+        }
     }
 }

common/src/main/java/io/netty/util/concurrent/DefaultPromise.java

@@ -17,7 +17,7 @@ package io.netty.util.concurrent;
 
 import io.netty.util.Signal;
 import io.netty.util.internal.EmptyArrays;
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.internal.InternalThreadLocalMap;
 import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.StringUtil;
 import io.netty.util.internal.logging.InternalLogger;
@@ -36,12 +36,6 @@ public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
             InternalLoggerFactory.getInstance(DefaultPromise.class.getName() + ".rejectedExecution");
 
     private static final int MAX_LISTENER_STACK_DEPTH = 8;
-    private static final ThreadLocal<Integer> LISTENER_STACK_DEPTH = new FastThreadLocal<Integer>() {
-        @Override
-        protected Integer initialValue() {
-            return 0;
-        }
-    };
     private static final Signal SUCCESS = Signal.valueOf(DefaultPromise.class, "SUCCESS");
     private static final Signal UNCANCELLABLE = Signal.valueOf(DefaultPromise.class, "UNCANCELLABLE");
     private static final CauseHolder CANCELLATION_CAUSE_HOLDER = new CauseHolder(new CancellationException());
@@ -557,9 +551,10 @@ public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
 
         EventExecutor executor = executor();
         if (executor.inEventLoop()) {
-            final Integer stackDepth = LISTENER_STACK_DEPTH.get();
+            final InternalThreadLocalMap threadLocals = InternalThreadLocalMap.get();
+            final int stackDepth = threadLocals.futureListenerStackDepth();
             if (stackDepth < MAX_LISTENER_STACK_DEPTH) {
-                LISTENER_STACK_DEPTH.set(stackDepth + 1);
+                threadLocals.setFutureListenerStackDepth(stackDepth + 1);
                 try {
                     if (listeners instanceof DefaultFutureListeners) {
                         notifyListeners0(this, (DefaultFutureListeners) listeners);
@@ -571,7 +566,7 @@ public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
                     }
                 } finally {
                     this.listeners = null;
-                    LISTENER_STACK_DEPTH.set(stackDepth);
+                    threadLocals.setFutureListenerStackDepth(stackDepth);
                 }
                 return;
             }
@@ -617,13 +612,14 @@ public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
         final EventExecutor executor = executor();
         if (executor.inEventLoop()) {
             if (listeners == null && lateListeners == null) {
-                final Integer stackDepth = LISTENER_STACK_DEPTH.get();
+                final InternalThreadLocalMap threadLocals = InternalThreadLocalMap.get();
+                final int stackDepth = threadLocals.futureListenerStackDepth();
                 if (stackDepth < MAX_LISTENER_STACK_DEPTH) {
-                    LISTENER_STACK_DEPTH.set(stackDepth + 1);
+                    threadLocals.setFutureListenerStackDepth(stackDepth + 1);
                     try {
                         notifyListener0(this, l);
                     } finally {
-                        LISTENER_STACK_DEPTH.set(stackDepth);
+                        threadLocals.setFutureListenerStackDepth(stackDepth);
                     }
                     return;
                 }
@@ -648,13 +644,14 @@ public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
             final EventExecutor eventExecutor, final Future<?> future, final GenericFutureListener<?> l) {
 
         if (eventExecutor.inEventLoop()) {
-            final Integer stackDepth = LISTENER_STACK_DEPTH.get();
+            final InternalThreadLocalMap threadLocals = InternalThreadLocalMap.get();
+            final int stackDepth = threadLocals.futureListenerStackDepth();
             if (stackDepth < MAX_LISTENER_STACK_DEPTH) {
-                LISTENER_STACK_DEPTH.set(stackDepth + 1);
+                threadLocals.setFutureListenerStackDepth(stackDepth + 1);
                 try {
                     notifyListener0(future, l);
                 } finally {
-                    LISTENER_STACK_DEPTH.set(stackDepth);
+                    threadLocals.setFutureListenerStackDepth(stackDepth);
                 }
                 return;
             }

common/src/main/java/io/netty/util/concurrent/DefaultThreadFactory.java

@@ -16,7 +16,6 @@
 
 package io.netty.util.concurrent;
 
-import io.netty.util.internal.FastThreadLocalThread;
 import io.netty.util.internal.StringUtil;
 
 import java.util.Locale;
@@ -99,7 +98,7 @@ public class DefaultThreadFactory implements ThreadFactory {
 
     @Override
     public Thread newThread(Runnable r) {
-        Thread t = newThread(r, prefix + nextId.incrementAndGet());
+        Thread t = newThread(new DefaultRunnableDecorator(r), prefix + nextId.incrementAndGet());
         try {
             if (t.isDaemon()) {
                 if (!daemon) {
@@ -123,4 +122,22 @@ public class DefaultThreadFactory implements ThreadFactory {
     protected Thread newThread(Runnable r, String name) {
         return new FastThreadLocalThread(r, name);
     }
+
+    private static final class DefaultRunnableDecorator implements Runnable {
+
+        private final Runnable r;
+
+        DefaultRunnableDecorator(Runnable r) {
+            this.r = r;
+        }
+
+        @Override
+        public void run() {
+            try {
+                r.run();
+            } finally {
+                FastThreadLocal.removeAll();
+            }
+        }
+    }
 }

common/src/main/java/io/netty/util/concurrent/FastThreadLocal.java

@@ -0,0 +1,244 @@
+/*
+ * Copyright 2014 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.util.concurrent;
+
+import io.netty.util.internal.InternalThreadLocalMap;
+import io.netty.util.internal.PlatformDependent;
+
+import java.util.Collections;
+import java.util.IdentityHashMap;
+import java.util.Set;
+
+/**
+ * A special variant of {@link ThreadLocal} that yields higher access performan when accessed from a
+ * {@link FastThreadLocalThread}.
+ * <p>
+ * Internally, a {@link FastThreadLocal} uses a constant index in an array, instead of using hash code and hash table,
+ * to look for a variable.  Although seemingly very subtle, it yields slight performance advantage over using a hash
+ * table, and it is useful when accessed frequently.
+ * </p><p>
+ * To take advantage of this thread-local variable, your thread must be a {@link FastThreadLocalThread} or its subtype.
+ * By default, all threads created by {@link DefaultThreadFactory} are {@link FastThreadLocalThread} due to this reason.
+ * </p><p>
+ * Note that the fast path is only possible on threads that extend {@link FastThreadLocalThread}, because it requires
+ * a special field to store the necessary state.  An access by any other kind of thread falls back to a regular
+ * {@link ThreadLocal}.
+ * </p>
+ *
+ * @param <V> the type of the thread-local variable
+ * @see ThreadLocal
+ */
+public class FastThreadLocal<V> {
+
+    private static final int variablesToRemoveIndex = InternalThreadLocalMap.nextVariableIndex();
+
+    /**
+     * Removes all {@link FastThreadLocal} variables bound to the current thread.  This operation is useful when you
+     * are in a container environment, and you don't want to leave the thread local variables in the threads you do not
+     * manage.
+     */
+    public static void removeAll() {
+        InternalThreadLocalMap threadLocalMap = InternalThreadLocalMap.getIfSet();
+        if (threadLocalMap == null) {
+            return;
+        }
+
+        try {
+            Object v = threadLocalMap.indexedVariable(variablesToRemoveIndex);
+            if (v != null && v != InternalThreadLocalMap.UNSET) {
+                @SuppressWarnings("unchecked")
+                Set<FastThreadLocal<?>> variablesToRemove = (Set<FastThreadLocal<?>>) v;
+                FastThreadLocal<?>[] variablesToRemoveArray =
+                        variablesToRemove.toArray(new FastThreadLocal[variablesToRemove.size()]);
+                for (FastThreadLocal<?> tlv: variablesToRemoveArray) {
+                    tlv.remove(threadLocalMap);
+                }
+            }
+        } finally {
+            InternalThreadLocalMap.remove();
+        }
+    }
+
+    /**
+     * Returns the number of thread local variables bound to the current thread.
+     */
+    public static int size() {
+        InternalThreadLocalMap threadLocalMap = InternalThreadLocalMap.getIfSet();
+        if (threadLocalMap == null) {
+            return 0;
+        } else {
+            return threadLocalMap.size();
+        }
+    }
+
+    /**
+     * Destroys the data structure that keeps all {@link FastThreadLocal} variables accessed from
+     * non-{@link FastThreadLocalThread}s.  This operation is useful when you are in a container environment, and you
+     * do not want to leave the thread local variables in the threads you do not manage.  Call this method when your
+     * application is being unloaded from the container.
+     */
+    public static void destroy() {
+        InternalThreadLocalMap.destroy();
+    }
+
+    @SuppressWarnings("unchecked")
+    private static void addToVariablesToRemove(InternalThreadLocalMap threadLocalMap, FastThreadLocal<?> variable) {
+        Object v = threadLocalMap.indexedVariable(variablesToRemoveIndex);
+        Set<FastThreadLocal<?>> variablesToRemove;
+        if (v == InternalThreadLocalMap.UNSET || v == null) {
+            variablesToRemove = Collections.newSetFromMap(new IdentityHashMap<FastThreadLocal<?>, Boolean>());
+            threadLocalMap.setIndexedVariable(variablesToRemoveIndex, variablesToRemove);
+        } else {
+            variablesToRemove = (Set<FastThreadLocal<?>>) v;
+        }
+
+        variablesToRemove.add(variable);
+    }
+
+    private static void removeFromVariablesToRemove(
+            InternalThreadLocalMap threadLocalMap, FastThreadLocal<?> variable) {
+
+        Object v = threadLocalMap.indexedVariable(variablesToRemoveIndex);
+
+        if (v == InternalThreadLocalMap.UNSET || v == null) {
+            return;
+        }
+
+        @SuppressWarnings("unchecked")
+        Set<FastThreadLocal<?>> variablesToRemove = (Set<FastThreadLocal<?>>) v;
+        variablesToRemove.remove(variable);
+    }
+
+    private final int index;
+
+    public FastThreadLocal() {
+        index = InternalThreadLocalMap.nextVariableIndex();
+    }
+
+    /**
+     * Returns the current value for the current thread
+     */
+    public final V get() {
+        return get(InternalThreadLocalMap.get());
+    }
+
+    /**
+     * Returns the current value for the specified thread local map.
+     * The specified thread local map must be for the current thread.
+     */
+    @SuppressWarnings("unchecked")
+    public final V get(InternalThreadLocalMap threadLocalMap) {
+        Object v = threadLocalMap.indexedVariable(index);
+        if (v != InternalThreadLocalMap.UNSET) {
+            return (V) v;
+        }
+
+        return initialize(threadLocalMap);
+    }
+
+    private V initialize(InternalThreadLocalMap threadLocalMap) {
+        V v = null;
+        try {
+            v = initialValue();
+        } catch (Exception e) {
+            PlatformDependent.throwException(e);
+        }
+
+        threadLocalMap.setIndexedVariable(index, v);
+        addToVariablesToRemove(threadLocalMap, this);
+        return v;
+    }
+
+    /**
+     * Set the value for the current thread.
+     */
+    public final void set(V value) {
+        if (value != InternalThreadLocalMap.UNSET) {
+            set(InternalThreadLocalMap.get(), value);
+        } else {
+            remove();
+        }
+    }
+
+    /**
+     * Set the value for the specified thread local map. The specified thread local map must be for the current thread.
+     */
+    public final void set(InternalThreadLocalMap threadLocalMap, V value) {
+        if (value != InternalThreadLocalMap.UNSET) {
+            if (threadLocalMap.setIndexedVariable(index, value)) {
+                addToVariablesToRemove(threadLocalMap, this);
+            }
+        } else {
+            remove(threadLocalMap);
+        }
+    }
+
+    /**
+     * Returns {@code true} if and only if this thread-local variable is set.
+     */
+    public final boolean isSet() {
+        return isSet(InternalThreadLocalMap.getIfSet());
+    }
+
+    /**
+     * Returns {@code true} if and only if this thread-local variable is set.
+     * The specified thread local map must be for the current thread.
+     */
+    public final boolean isSet(InternalThreadLocalMap threadLocalMap) {
+        return threadLocalMap != null && threadLocalMap.isIndexedVariableSet(index);
+    }
+    /**
+     * Sets the value to uninitialized; a proceeding call to get() will trigger a call to initialValue().
+     */
+    public final void remove() {
+        remove(InternalThreadLocalMap.getIfSet());
+    }
+
+    /**
+     * Sets the value to uninitialized for the specified thread local map;
+     * a proceeding call to get() will trigger a call to initialValue().
+     * The specified thread local map must be for the current thread.
+     */
+    @SuppressWarnings("unchecked")
+    public final void remove(InternalThreadLocalMap threadLocalMap) {
+        if (threadLocalMap == null) {
+            return;
+        }
+
+        Object v = threadLocalMap.removeIndexedVariable(index);
+        removeFromVariablesToRemove(threadLocalMap, this);
+
+        if (v != InternalThreadLocalMap.UNSET) {
+            try {
+                onRemoval((V) v);
+            } catch (Exception e) {
+                PlatformDependent.throwException(e);
+            }
+        }
+    }
+
+    /**
+     * Returns the initial value for this thread-local variable.
+     */
+    protected V initialValue() throws Exception {
+        return null;
+    }
+
+    /**
+     * Invoked when this thread local variable is removed by {@link #remove()}.
+     */
+    protected void onRemoval(@SuppressWarnings("UnusedParameters") V value) throws Exception { }
+}

common/src/main/java/io/netty/util/concurrent/FastThreadLocalThread.java

@@ -13,17 +13,16 @@
 * License for the specific language governing permissions and limitations
 * under the License.
 */
-package io.netty.util.internal;
+package io.netty.util.concurrent;
 
-import java.util.Arrays;
+import io.netty.util.internal.InternalThreadLocalMap;
 
 /**
- * To utilise the {@link FastThreadLocal} fast-path, all threads accessing a {@link FastThreadLocal} must extend this
- * class.
+ * A special {@link Thread} that provides fast access to {@link FastThreadLocal} variables.
  */
 public class FastThreadLocalThread extends Thread {
 
-    Object[] lookup = newArray();
+    private InternalThreadLocalMap threadLocalMap;
 
     public FastThreadLocalThread() { }
 
@@ -55,28 +54,19 @@ public class FastThreadLocalThread extends Thread {
         super(group, target, name, stackSize);
     }
 
-    private static Object[] newArray() {
-        Object[] array = new Object[32];
-        Arrays.fill(array, FastThreadLocal.EMPTY);
-        return array;
+    /**
+     * Returns the internal data structure that keeps the thread-local variables bound to this thread.
+     * Note that this method is for internal use only, and thus is subject to change at any time.
+     */
+    public final InternalThreadLocalMap threadLocalMap() {
+        return threadLocalMap;
     }
 
-    Object[] expandArray(int length) {
-        int newCapacity = lookup.length;
-        do {
-            // double capacity until it is big enough
-            newCapacity <<= 1;
-
-            if (newCapacity < 0) {
-                throw new IllegalStateException();
-            }
-
-        } while (length > newCapacity);
-
-        Object[] array = new Object[newCapacity];
-        System.arraycopy(lookup, 0, array, 0, lookup.length);
-        Arrays.fill(array, lookup.length, array.length, FastThreadLocal.EMPTY);
-        lookup = array;
-        return lookup;
+    /**
+     * Sets the internal data structure that keeps the thread-local variables bound to this thread.
+     * Note that this method is for internal use only, and thus is subject to change at any time.
+     */
+    public final void setThreadLocalMap(InternalThreadLocalMap threadLocalMap) {
+        this.threadLocalMap = threadLocalMap;
     }
 }

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

@@ -1,112 +0,0 @@
-/*
- * Copyright 2014 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.util.internal;
-
-import java.util.concurrent.atomic.AtomicInteger;
-
-/**
- * A special {@link ThreadLocal} which is operating over a predefined array, so it always operate in O(1) when called
- * from a {@link FastThreadLocalThread}. This permits less indirection and offers a slight performance improvement,
- * so is useful when invoked frequently.
- *
- * The fast path is only possible on threads that extend FastThreadLocalThread, as this class
- * stores the necessary state. Access by any other kind of thread falls back to a regular ThreadLocal
- *
- * @param <V>
- */
-public class FastThreadLocal<V> extends ThreadLocal<V> {
-    static final Object EMPTY = new Object();
-
-    private static final AtomicInteger NEXT_INDEX = new AtomicInteger(0);
-    private final ThreadLocal<V> fallback = new ThreadLocal<V>() {
-        @Override
-        protected V initialValue() {
-            return FastThreadLocal.this.initialValue();
-        }
-    };
-    private final int index;
-
-    public FastThreadLocal() {
-        index = NEXT_INDEX.getAndIncrement();
-        if (index < 0) {
-            NEXT_INDEX.decrementAndGet();
-            throw new IllegalStateException("Maximal number (" + Integer.MAX_VALUE + ") of FastThreadLocal exceeded");
-        }
-    }
-
-    /**
-     * Set the value for the current thread
-     */
-    @Override
-    public void set(V value) {
-        Thread thread = Thread.currentThread();
-        if (!(thread instanceof FastThreadLocalThread)) {
-            fallback.set(value);
-            return;
-        }
-        FastThreadLocalThread fastThread = (FastThreadLocalThread) thread;
-        Object[] lookup = fastThread.lookup;
-        if (index >= lookup.length) {
-            lookup = fastThread.expandArray(index);
-        }
-        lookup[index] = value;
-    }
-
-    /**
-     * Sets the value to uninitialized; a proceeding call to get() will trigger a call to initialValue()
-     */
-    @Override
-    public void remove() {
-        Thread thread = Thread.currentThread();
-        if (!(thread instanceof FastThreadLocalThread)) {
-            fallback.remove();
-            return;
-        }
-        Object[] lookup = ((FastThreadLocalThread) thread).lookup;
-        if (index >= lookup.length) {
-            return;
-        }
-        lookup[index] = EMPTY;
-    }
-
-    /**
-     * @return the current value for the current thread
-     */
-    @Override
-    @SuppressWarnings("unchecked")
-    public V get() {
-        Thread thread = Thread.currentThread();
-        if (!(thread instanceof FastThreadLocalThread)) {
-            return fallback.get();
-        }
-        FastThreadLocalThread fastThread = (FastThreadLocalThread) thread;
-
-        Object[] lookup = fastThread.lookup;
-        Object v;
-        if (index >= lookup.length) {
-            v = initialValue();
-            lookup = fastThread.expandArray(index);
-            lookup[index] = v;
-        } else {
-            v = lookup[index];
-            if (v == EMPTY) {
-                v = initialValue();
-                lookup[index] = v;
-            }
-        }
-        return (V) v;
-    }
-}

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

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2014 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.util.internal;
+
+public final class IntegerHolder {
+    public int value;
+}

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

@@ -0,0 +1,310 @@
+/*
+ * Copyright 2014 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.util.internal;
+
+import io.netty.util.concurrent.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocalThread;
+
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CharsetEncoder;
+import java.util.Arrays;
+import java.util.IdentityHashMap;
+import java.util.Map;
+import java.util.WeakHashMap;
+
+/**
+ * The internal data structure that stores the thread-local variables for Netty and all {@link FastThreadLocal}s.
+ * Note that this class is for internal use only and is subject to change at any time.  Use {@link FastThreadLocal}
+ * unless you know what you are doing.
+ */
+public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap {
+
+    public static final Object UNSET = new Object();
+
+    public static InternalThreadLocalMap getIfSet() {
+        Thread thread = Thread.currentThread();
+        InternalThreadLocalMap threadLocalMap;
+        if (thread instanceof FastThreadLocalThread) {
+            threadLocalMap = ((FastThreadLocalThread) thread).threadLocalMap();
+        } else {
+            ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = UnpaddedInternalThreadLocalMap.slowThreadLocalMap;
+            if (slowThreadLocalMap == null) {
+                threadLocalMap = null;
+            } else {
+                threadLocalMap = slowThreadLocalMap.get();
+            }
+        }
+        return threadLocalMap;
+    }
+
+    public static InternalThreadLocalMap get() {
+        Thread thread = Thread.currentThread();
+        if (thread instanceof FastThreadLocalThread) {
+            return fastGet((FastThreadLocalThread) thread);
+        } else {
+            return slowGet();
+        }
+    }
+
+    private static InternalThreadLocalMap fastGet(FastThreadLocalThread thread) {
+        InternalThreadLocalMap threadLocalMap = thread.threadLocalMap();
+        if (threadLocalMap == null) {
+            thread.setThreadLocalMap(threadLocalMap = new InternalThreadLocalMap());
+        }
+        return threadLocalMap;
+    }
+
+    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();
+            slowThreadLocalMap.set(ret);
+        }
+        return ret;
+    }
+
+    public static void remove() {
+        Thread thread = Thread.currentThread();
+        if (thread instanceof FastThreadLocalThread) {
+            ((FastThreadLocalThread) thread).setThreadLocalMap(null);
+        } else {
+            ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = UnpaddedInternalThreadLocalMap.slowThreadLocalMap;
+            if (slowThreadLocalMap != null) {
+                slowThreadLocalMap.remove();
+            }
+        }
+    }
+
+    public static void destroy() {
+        slowThreadLocalMap = null;
+    }
+
+    public static int nextVariableIndex() {
+        int index = nextIndex.getAndIncrement();
+        if (index < 0) {
+            nextIndex.decrementAndGet();
+            throw new IllegalStateException("too many thread-local indexed variables");
+        }
+        return index;
+    }
+
+    public static int lastVariableIndex() {
+        return nextIndex.get() - 1;
+    }
+
+    // Cache line padding (must be public)
+    // With CompressedOops enabled, an instance of this class should occupy at least 128 bytes.
+    public long rp1, rp2, rp3, rp4, rp5, rp6, rp7, rp8, rp9;
+
+    private InternalThreadLocalMap() {
+        super(newIndexedVariableTable());
+    }
+
+    private static Object[] newIndexedVariableTable() {
+        Object[] array = new Object[32];
+        Arrays.fill(array, UNSET);
+        return array;
+    }
+
+    public int size() {
+        int count = 0;
+
+        if (futureListenerStackDepth != 0) {
+            count ++;
+        }
+        if (localChannelReaderStackDepth != 0) {
+            count ++;
+        }
+        if (handlerSharableCache != null) {
+            count ++;
+        }
+        if (counterHashCode != null) {
+            count ++;
+        }
+        if (random != null) {
+            count ++;
+        }
+        if (typeParameterMatcherGetCache != null) {
+            count ++;
+        }
+        if (typeParameterMatcherFindCache != null) {
+            count ++;
+        }
+        if (stringBuilder != null) {
+            count ++;
+        }
+        if (charsetEncoderCache != null) {
+            count ++;
+        }
+        if (charsetDecoderCache != null) {
+            count ++;
+        }
+
+        for (Object o: indexedVariables) {
+            if (o != UNSET) {
+                count ++;
+            }
+        }
+
+        // We should subtract 1 from the count because the first element in 'indexedVariables' is reserved
+        // by 'FastThreadLocal' to keep the list of 'FastThreadLocal's to remove on 'FastThreadLocal.removeAll()'.
+        return count - 1;
+    }
+
+    public StringBuilder stringBuilder() {
+        StringBuilder builder = stringBuilder;
+        if (builder == null) {
+            stringBuilder = builder = new StringBuilder(512);
+        } else {
+            builder.setLength(0);
+        }
+        return builder;
+    }
+
+    public Map<Charset, CharsetEncoder> charsetEncoderCache() {
+        Map<Charset, CharsetEncoder> cache = charsetEncoderCache;
+        if (cache == null) {
+            charsetEncoderCache = cache = new IdentityHashMap<Charset, CharsetEncoder>();
+        }
+        return cache;
+    }
+
+    public Map<Charset, CharsetDecoder> charsetDecoderCache() {
+        Map<Charset, CharsetDecoder> cache = charsetDecoderCache;
+        if (cache == null) {
+            charsetDecoderCache = cache = new IdentityHashMap<Charset, CharsetDecoder>();
+        }
+        return cache;
+    }
+
+    public int futureListenerStackDepth() {
+        return futureListenerStackDepth;
+    }
+
+    public void setFutureListenerStackDepth(int futureListenerStackDepth) {
+        this.futureListenerStackDepth = futureListenerStackDepth;
+    }
+
+    public ThreadLocalRandom random() {
+        ThreadLocalRandom r = random;
+        if (r == null) {
+            random = r = new ThreadLocalRandom();
+        }
+        return r;
+    }
+
+    public Map<Class<?>, TypeParameterMatcher> typeParameterMatcherGetCache() {
+        Map<Class<?>, TypeParameterMatcher> cache = typeParameterMatcherGetCache;
+        if (cache == null) {
+            typeParameterMatcherGetCache = cache = new IdentityHashMap<Class<?>, TypeParameterMatcher>();
+        }
+        return cache;
+    }
+
+    public Map<Class<?>, Map<String, TypeParameterMatcher>> typeParameterMatcherFindCache() {
+        Map<Class<?>, Map<String, TypeParameterMatcher>> cache = typeParameterMatcherFindCache;
+        if (cache == null) {
+            typeParameterMatcherFindCache = cache = new IdentityHashMap<Class<?>, Map<String, TypeParameterMatcher>>();
+        }
+        return cache;
+    }
+
+    public IntegerHolder counterHashCode() {
+        return counterHashCode;
+    }
+
+    public void setCounterHashCode(IntegerHolder counterHashCode) {
+        this.counterHashCode = counterHashCode;
+    }
+
+    public Map<Class<?>, Boolean> handlerSharableCache() {
+        Map<Class<?>, Boolean> cache = handlerSharableCache;
+        if (cache == null) {
+            // Start with small capacity to keep memory overhead as low as possible.
+            handlerSharableCache = cache = new WeakHashMap<Class<?>, Boolean>(4);
+        }
+        return cache;
+    }
+
+    public int localChannelReaderStackDepth() {
+        return localChannelReaderStackDepth;
+    }
+
+    public void setLocalChannelReaderStackDepth(int localChannelReaderStackDepth) {
+        this.localChannelReaderStackDepth = localChannelReaderStackDepth;
+    }
+
+    public Object indexedVariable(int index) {
+        Object[] lookup = indexedVariables;
+        return index < lookup.length? lookup[index] : UNSET;
+    }
+
+    /**
+     * @return {@code true} if and only if a new thread-local variable has been created
+     */
+    public boolean setIndexedVariable(int index, Object value) {
+        Object[] lookup = indexedVariables;
+        if (index < lookup.length) {
+            Object oldValue = lookup[index];
+            lookup[index] = value;
+            return oldValue == UNSET;
+        } else {
+            expandIndexedVariableTableAndSet(index, value);
+            return true;
+        }
+    }
+
+    private void expandIndexedVariableTableAndSet(int index, Object value) {
+        Object[] oldArray = indexedVariables;
+        final int oldCapacity = oldArray.length;
+        int newCapacity = index;
+        newCapacity |= newCapacity >>>  1;
+        newCapacity |= newCapacity >>>  2;
+        newCapacity |= newCapacity >>>  4;
+        newCapacity |= newCapacity >>>  8;
+        newCapacity |= newCapacity >>> 16;
+        newCapacity ++;
+
+        Object[] newArray = Arrays.copyOf(oldArray, newCapacity);
+        Arrays.fill(newArray, oldCapacity, newArray.length, UNSET);
+        newArray[index] = value;
+        indexedVariables = newArray;
+    }
+
+    public Object removeIndexedVariable(int index) {
+        Object[] lookup = indexedVariables;
+        if (index < lookup.length) {
+            Object v = lookup[index];
+            lookup[index] = UNSET;
+            return v;
+        } else {
+            return UNSET;
+        }
+    }
+
+    public boolean isIndexedVariableSet(int index) {
+        Object[] lookup = indexedVariables;
+        return index < lookup.length && lookup[index] != UNSET;
+    }
+}

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

@@ -58,7 +58,7 @@ import java.util.concurrent.atomic.AtomicLong;
  * //author Doug Lea
  */
 @SuppressWarnings("all")
-public class ThreadLocalRandom extends Random {
+public final class ThreadLocalRandom extends Random {
 
     private static final InternalLogger logger = InternalLoggerFactory.getInstance(ThreadLocalRandom.class);
 
@@ -203,23 +203,13 @@ public class ThreadLocalRandom extends Random {
         initialized = true;
     }
 
-    /**
-     * The actual ThreadLocal
-     */
-    private static final ThreadLocal<ThreadLocalRandom> localRandom =
-            new FastThreadLocal<ThreadLocalRandom>() {
-                protected ThreadLocalRandom initialValue() {
-                    return new ThreadLocalRandom();
-                }
-            };
-
     /**
      * Returns the current thread's {@code ThreadLocalRandom}.
      *
      * @return the current thread's {@code ThreadLocalRandom}
      */
     public static ThreadLocalRandom current() {
-        return localRandom.get();
+        return InternalThreadLocalMap.get().random();
     }
 
     /**

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

@@ -22,7 +22,6 @@ import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.lang.reflect.TypeVariable;
 import java.util.HashMap;
-import java.util.IdentityHashMap;
 import java.util.Map;
 
 public abstract class TypeParameterMatcher {
@@ -30,16 +29,9 @@ public abstract class TypeParameterMatcher {
     private static final TypeParameterMatcher NOOP = new NoOpTypeParameterMatcher();
     private static final Object TEST_OBJECT = new Object();
 
-    private static final ThreadLocal<Map<Class<?>, TypeParameterMatcher>> getCache =
-            new FastThreadLocal<Map<Class<?>, TypeParameterMatcher>>() {
-                @Override
-                protected Map<Class<?>, TypeParameterMatcher> initialValue() {
-                    return new IdentityHashMap<Class<?>, TypeParameterMatcher>();
-                }
-            };
-
     public static TypeParameterMatcher get(final Class<?> parameterType) {
-        final Map<Class<?>, TypeParameterMatcher> getCache = TypeParameterMatcher.getCache.get();
+        final Map<Class<?>, TypeParameterMatcher> getCache =
+                InternalThreadLocalMap.get().typeParameterMatcherGetCache();
 
         TypeParameterMatcher matcher = getCache.get(parameterType);
         if (matcher == null) {
@@ -68,18 +60,11 @@ public abstract class TypeParameterMatcher {
         return matcher;
     }
 
-    private static final ThreadLocal<Map<Class<?>, Map<String, TypeParameterMatcher>>> findCache =
-            new FastThreadLocal<Map<Class<?>, Map<String, TypeParameterMatcher>>>() {
-                @Override
-                protected Map<Class<?>, Map<String, TypeParameterMatcher>> initialValue() {
-                    return new IdentityHashMap<Class<?>, Map<String, TypeParameterMatcher>>();
-                }
-            };
-
     public static TypeParameterMatcher find(
             final Object object, final Class<?> parameterizedSuperclass, final String typeParamName) {
 
-        final Map<Class<?>, Map<String, TypeParameterMatcher>> findCache = TypeParameterMatcher.findCache.get();
+        final Map<Class<?>, Map<String, TypeParameterMatcher>> findCache =
+                InternalThreadLocalMap.get().typeParameterMatcherFindCache();
         final Class<?> thisClass = object.getClass();
 
         Map<String, TypeParameterMatcher> map = findCache.get(thisClass);

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

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2014 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.util.internal;
+
+import io.netty.util.concurrent.FastThreadLocal;
+
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CharsetEncoder;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * The internal data structure that stores the thread-local variables for Netty and all {@link FastThreadLocal}s.
+ * Note that this class is for internal use only and is subject to change at any time.  Use {@link FastThreadLocal}
+ * unless you know what you are doing.
+ */
+class UnpaddedInternalThreadLocalMap {
+
+    static ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap;
+    static final AtomicInteger nextIndex = new AtomicInteger();
+
+    /** Used by {@link FastThreadLocal} */
+    Object[] indexedVariables;
+
+    // Core thread-locals
+    int futureListenerStackDepth;
+    int localChannelReaderStackDepth;
+    Map<Class<?>, Boolean> handlerSharableCache;
+    IntegerHolder counterHashCode;
+    ThreadLocalRandom random;
+    Map<Class<?>, TypeParameterMatcher> typeParameterMatcherGetCache;
+    Map<Class<?>, Map<String, TypeParameterMatcher>> typeParameterMatcherFindCache;
+
+    // String-related thread-locals
+    StringBuilder stringBuilder;
+    Map<Charset, CharsetEncoder> charsetEncoderCache;
+    Map<Charset, CharsetDecoder> charsetDecoderCache;
+
+    UnpaddedInternalThreadLocalMap(Object[] indexedVariables) {
+        this.indexedVariables = indexedVariables;
+    }
+}

common/src/main/java/io/netty/util/internal/chmv8/ConcurrentHashMapV8.java

@@ -22,7 +22,8 @@
 
 package io.netty.util.internal.chmv8;
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.internal.IntegerHolder;
+import io.netty.util.internal.InternalThreadLocalMap;
 
 import java.io.ObjectStreamField;
 import java.io.Serializable;
@@ -2238,14 +2239,15 @@ public class ConcurrentHashMapV8<K,V>
         CounterCell[] as; long b, s;
         if ((as = counterCells) != null ||
                 !U.compareAndSwapLong(this, BASECOUNT, b = baseCount, s = b + x)) {
-            CounterHashCode hc; CounterCell a; long v; int m;
+            IntegerHolder hc; CounterCell a; long v; int m;
             boolean uncontended = true;
-            if ((hc = threadCounterHashCode.get()) == null ||
+            InternalThreadLocalMap threadLocals = InternalThreadLocalMap.get();
+            if ((hc = threadLocals.counterHashCode()) == null ||
                     as == null || (m = as.length - 1) < 0 ||
-                    (a = as[m & hc.code]) == null ||
+                    (a = as[m & hc.value]) == null ||
                     !(uncontended =
                             U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))) {
-                fullAddCount(x, hc, uncontended);
+                fullAddCount(threadLocals, x, hc, uncontended);
                 return;
             }
             if (check <= 1)
@@ -6030,13 +6032,6 @@ public class ConcurrentHashMapV8<K,V>
      */
     static final int SEED_INCREMENT = 0x61c88647;
 
-    /**
-     * Per-thread counter hash codes. Shared across all instances.
-     */
-    static final ThreadLocal<CounterHashCode> threadCounterHashCode =
-            new FastThreadLocal<CounterHashCode>();
-
-
     final long sumCount() {
         CounterCell[] as = counterCells; CounterCell a;
         long sum = baseCount;
@@ -6050,17 +6045,18 @@ public class ConcurrentHashMapV8<K,V>
     }
 
     // See LongAdder version for explanation
-    private final void fullAddCount(long x, CounterHashCode hc,
+    private final void fullAddCount(InternalThreadLocalMap threadLocals,
+                                    long x, IntegerHolder hc,
                                     boolean wasUncontended) {
         int h;
         if (hc == null) {
-            hc = new CounterHashCode();
+            hc = new IntegerHolder();
             int s = counterHashCodeGenerator.addAndGet(SEED_INCREMENT);
-            h = hc.code = (s == 0) ? 1 : s; // Avoid zero
-            threadCounterHashCode.set(hc);
+            h = hc.value = (s == 0) ? 1 : s; // Avoid zero
+            threadLocals.setCounterHashCode(hc);
         }
         else
-            h = hc.code;
+            h = hc.value;
         boolean collide = false;                // True if last slot nonempty
         for (;;) {
             CounterCell[] as; CounterCell a; int n; long v;
@@ -6135,7 +6131,7 @@ public class ConcurrentHashMapV8<K,V>
             else if (U.compareAndSwapLong(this, BASECOUNT, v = baseCount, v + x))
                 break;                          // Fall back on using base
         }
-        hc.code = h;                            // Record index for next time
+        hc.value = h;                           // Record index for next time
     }
 
     // Unsafe mechanics

common/src/main/java/io/netty/util/internal/chmv8/LongAdder.java

@@ -1,217 +0,0 @@
-/*
- * Copyright 2013 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.
- */
-
-/*
- * Written by Doug Lea with assistance from members of JCP JSR-166
- * Expert Group and released to the public domain, as explained at
- * http://creativecommons.org/publicdomain/zero/1.0/
- */
-
-package io.netty.util.internal.chmv8;
-
-import java.io.Serializable;
-import java.util.concurrent.atomic.AtomicLong;
-
-/**
- * One or more variables that together maintain an initially zero
- * {@code long} sum.  When updates (method {@link #add}) are contended
- * across threads, the set of variables may grow dynamically to reduce
- * contention. Method {@link #sum} (or, equivalently, {@link
- * #longValue}) returns the current total combined across the
- * variables maintaining the sum.
- *
- * <p>This class is usually preferable to {@link AtomicLong} when
- * multiple threads update a common sum that is used for purposes such
- * as collecting statistics, not for fine-grained synchronization
- * control.  Under low update contention, the two classes have similar
- * characteristics. But under high contention, expected throughput of
- * this class is significantly higher, at the expense of higher space
- * consumption.
- *
- * <p>This class extends {@link Number}, but does <em>not</em> define
- * methods such as {@code equals}, {@code hashCode} and {@code
- * compareTo} because instances are expected to be mutated, and so are
- * not useful as collection keys.
- *
- * <p><em>jsr166e note: This class is targeted to be placed in
- * java.util.concurrent.atomic.</em>
- *
- * @since 1.8
- * @author Doug Lea
- */
-@SuppressWarnings("all")
-public class LongAdder extends Striped64 implements Serializable {
-    private static final long serialVersionUID = 7249069246863182397L;
-
-    /**
-     * Version of plus for use in retryUpdate
-     */
-    final long fn(long v, long x) { return v + x; }
-
-    /**
-     * Creates a new adder with initial sum of zero.
-     */
-    public LongAdder() {
-    }
-
-    /**
-     * Adds the given value.
-     *
-     * @param x the value to add
-     */
-    public void add(long x) {
-        Cell[] as; long b, v; HashCode hc; Cell a; int n;
-        if ((as = cells) != null || !casBase(b = base, b + x)) {
-            boolean uncontended = true;
-            int h = (hc = threadHashCode.get()).code;
-            if (as == null || (n = as.length) < 1 ||
-                    (a = as[(n - 1) & h]) == null ||
-                    !(uncontended = a.cas(v = a.value, v + x)))
-                retryUpdate(x, hc, uncontended);
-        }
-    }
-
-    /**
-     * Equivalent to {@code add(1)}.
-     */
-    public void increment() {
-        add(1L);
-    }
-
-    /**
-     * Equivalent to {@code add(-1)}.
-     */
-    public void decrement() {
-        add(-1L);
-    }
-
-    /**
-     * Returns the current sum.  The returned value is <em>NOT</em> an
-     * atomic snapshot; invocation in the absence of concurrent
-     * updates returns an accurate result, but concurrent updates that
-     * occur while the sum is being calculated might not be
-     * incorporated.
-     *
-     * @return the sum
-     */
-    public long sum() {
-        long sum = base;
-        Cell[] as = cells;
-        if (as != null) {
-            int n = as.length;
-            for (int i = 0; i < n; ++i) {
-                Cell a = as[i];
-                if (a != null)
-                    sum += a.value;
-            }
-        }
-        return sum;
-    }
-
-    /**
-     * Resets variables maintaining the sum to zero.  This method may
-     * be a useful alternative to creating a new adder, but is only
-     * effective if there are no concurrent updates.  Because this
-     * method is intrinsically racy, it should only be used when it is
-     * known that no threads are concurrently updating.
-     */
-    public void reset() {
-        internalReset(0L);
-    }
-
-    /**
-     * Equivalent in effect to {@link #sum} followed by {@link
-     * #reset}. This method may apply for example during quiescent
-     * points between multithreaded computations.  If there are
-     * updates concurrent with this method, the returned value is
-     * <em>not</em> guaranteed to be the final value occurring before
-     * the reset.
-     *
-     * @return the sum
-     */
-    public long sumThenReset() {
-        long sum = base;
-        Cell[] as = cells;
-        base = 0L;
-        if (as != null) {
-            int n = as.length;
-            for (int i = 0; i < n; ++i) {
-                Cell a = as[i];
-                if (a != null) {
-                    sum += a.value;
-                    a.value = 0L;
-                }
-            }
-        }
-        return sum;
-    }
-
-    /**
-     * Returns the String representation of the {@link #sum}.
-     * @return the String representation of the {@link #sum}
-     */
-    public String toString() {
-        return Long.toString(sum());
-    }
-
-    /**
-     * Equivalent to {@link #sum}.
-     *
-     * @return the sum
-     */
-    public long longValue() {
-        return sum();
-    }
-
-    /**
-     * Returns the {@link #sum} as an {@code int} after a narrowing
-     * primitive conversion.
-     */
-    public int intValue() {
-        return (int)sum();
-    }
-
-    /**
-     * Returns the {@link #sum} as a {@code float}
-     * after a widening primitive conversion.
-     */
-    public float floatValue() {
-        return (float)sum();
-    }
-
-    /**
-     * Returns the {@link #sum} as a {@code double} after a widening
-     * primitive conversion.
-     */
-    public double doubleValue() {
-        return (double)sum();
-    }
-
-    private void writeObject(java.io.ObjectOutputStream s)
-            throws java.io.IOException {
-        s.defaultWriteObject();
-        s.writeLong(sum());
-    }
-
-    private void readObject(java.io.ObjectInputStream s)
-            throws java.io.IOException, ClassNotFoundException {
-        s.defaultReadObject();
-        busy = 0;
-        cells = null;
-        base = s.readLong();
-    }
-
-}

common/src/main/java/io/netty/util/internal/chmv8/Striped64.java

@@ -1,359 +0,0 @@
-/*
- * Copyright 2013 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.
- */
-
-/*
- * Written by Doug Lea with assistance from members of JCP JSR-166
- * Expert Group and released to the public domain, as explained at
- * http://creativecommons.org/publicdomain/zero/1.0/
- */
-
-package io.netty.util.internal.chmv8;
-
-import java.util.Random;
-
-/**
- * A package-local class holding common representation and mechanics
- * for classes supporting dynamic striping on 64bit values. The class
- * extends Number so that concrete subclasses must publicly do so.
- */
-@SuppressWarnings("all")
-abstract class Striped64 extends Number {
-    /*
-     * This class maintains a lazily-initialized table of atomically
-     * updated variables, plus an extra "base" field. The table size
-     * is a power of two. Indexing uses masked per-thread hash codes.
-     * Nearly all declarations in this class are package-private,
-     * accessed directly by subclasses.
-     *
-     * Table entries are of class Cell; a variant of AtomicLong padded
-     * to reduce cache contention on most processors. Padding is
-     * overkill for most Atomics because they are usually irregularly
-     * scattered in memory and thus don't interfere much with each
-     * other. But Atomic objects residing in arrays will tend to be
-     * placed adjacent to each other, and so will most often share
-     * cache lines (with a huge negative performance impact) without
-     * this precaution.
-     *
-     * In part because Cells are relatively large, we avoid creating
-     * them until they are needed.  When there is no contention, all
-     * updates are made to the base field.  Upon first contention (a
-     * failed CAS on base update), the table is initialized to size 2.
-     * The table size is doubled upon further contention until
-     * reaching the nearest power of two greater than or equal to the
-     * number of CPUS. Table slots remain empty (null) until they are
-     * needed.
-     *
-     * A single spinlock ("busy") is used for initializing and
-     * resizing the table, as well as populating slots with new Cells.
-     * There is no need for a blocking lock; when the lock is not
-     * available, threads try other slots (or the base).  During these
-     * retries, there is increased contention and reduced locality,
-     * which is still better than alternatives.
-     *
-     * Per-thread hash codes are initialized to random values.
-     * Contention and/or table collisions are indicated by failed
-     * CASes when performing an update operation (see method
-     * retryUpdate). Upon a collision, if the table size is less than
-     * the capacity, it is doubled in size unless some other thread
-     * holds the lock. If a hashed slot is empty, and lock is
-     * available, a new Cell is created. Otherwise, if the slot
-     * exists, a CAS is tried.  Retries proceed by "double hashing",
-     * using a secondary hash (Marsaglia XorShift) to try to find a
-     * free slot.
-     *
-     * The table size is capped because, when there are more threads
-     * than CPUs, supposing that each thread were bound to a CPU,
-     * there would exist a perfect hash function mapping threads to
-     * slots that eliminates collisions. When we reach capacity, we
-     * search for this mapping by randomly varying the hash codes of
-     * colliding threads.  Because search is random, and collisions
-     * only become known via CAS failures, convergence can be slow,
-     * and because threads are typically not bound to CPUS forever,
-     * may not occur at all. However, despite these limitations,
-     * observed contention rates are typically low in these cases.
-     *
-     * It is possible for a Cell to become unused when threads that
-     * once hashed to it terminate, as well as in the case where
-     * doubling the table causes no thread to hash to it under
-     * expanded mask.  We do not try to detect or remove such cells,
-     * under the assumption that for long-running instances, observed
-     * contention levels will recur, so the cells will eventually be
-     * needed again; and for short-lived ones, it does not matter.
-     */
-
-    /**
-     * Padded variant of AtomicLong supporting only raw accesses plus CAS.
-     * The value field is placed between pads, hoping that the JVM doesn't
-     * reorder them.
-     *
-     * JVM intrinsics note: It would be possible to use a release-only
-     * form of CAS here, if it were provided.
-     */
-    static final class Cell {
-        volatile long p0, p1, p2, p3, p4, p5, p6;
-        volatile long value;
-        volatile long q0, q1, q2, q3, q4, q5, q6;
-        Cell(long x) { value = x; }
-
-        final boolean cas(long cmp, long val) {
-            return UNSAFE.compareAndSwapLong(this, valueOffset, cmp, val);
-        }
-
-        // Unsafe mechanics
-        private static final sun.misc.Unsafe UNSAFE;
-        private static final long valueOffset;
-        static {
-            try {
-                UNSAFE = getUnsafe();
-                Class<?> ak = Cell.class;
-                valueOffset = UNSAFE.objectFieldOffset
-                        (ak.getDeclaredField("value"));
-            } catch (Exception e) {
-                throw new Error(e);
-            }
-        }
-
-    }
-
-    /**
-     * Holder for the thread-local hash code. The code is initially
-     * random, but may be set to a different value upon collisions.
-     */
-    static final class HashCode {
-        static final Random rng = new Random();
-        int code;
-        HashCode() {
-            int h = rng.nextInt(); // Avoid zero to allow xorShift rehash
-            code = (h == 0) ? 1 : h;
-        }
-    }
-
-    /**
-     * The corresponding ThreadLocal class
-     */
-    static final class ThreadHashCode extends ThreadLocal<HashCode> {
-        public HashCode initialValue() { return new HashCode(); }
-    }
-
-    /**
-     * Static per-thread hash codes. Shared across all instances to
-     * reduce ThreadLocal pollution and because adjustments due to
-     * collisions in one table are likely to be appropriate for
-     * others.
-     */
-    static final ThreadHashCode threadHashCode = new ThreadHashCode();
-
-    /** Number of CPUS, to place bound on table size */
-    static final int NCPU = Runtime.getRuntime().availableProcessors();
-
-    /**
-     * Table of cells. When non-null, size is a power of 2.
-     */
-    transient volatile Cell[] cells;
-
-    /**
-     * Base value, used mainly when there is no contention, but also as
-     * a fallback during table initialization races. Updated via CAS.
-     */
-    transient volatile long base;
-
-    /**
-     * Spinlock (locked via CAS) used when resizing and/or creating Cells.
-     */
-    transient volatile int busy;
-
-    /**
-     * Package-private default constructor
-     */
-    Striped64() {
-    }
-
-    /**
-     * CASes the base field.
-     */
-    final boolean casBase(long cmp, long val) {
-        return UNSAFE.compareAndSwapLong(this, baseOffset, cmp, val);
-    }
-
-    /**
-     * CASes the busy field from 0 to 1 to acquire lock.
-     */
-    final boolean casBusy() {
-        return UNSAFE.compareAndSwapInt(this, busyOffset, 0, 1);
-    }
-
-    /**
-     * Computes the function of current and new value. Subclasses
-     * should open-code this update function for most uses, but the
-     * virtualized form is needed within retryUpdate.
-     *
-     * @param currentValue the current value (of either base or a cell)
-     * @param newValue the argument from a user update call
-     * @return result of the update function
-     */
-    abstract long fn(long currentValue, long newValue);
-
-    /**
-     * Handles cases of updates involving initialization, resizing,
-     * creating new Cells, and/or contention. See above for
-     * explanation. This method suffers the usual non-modularity
-     * problems of optimistic retry code, relying on rechecked sets of
-     * reads.
-     *
-     * @param x the value
-     * @param hc the hash code holder
-     * @param wasUncontended false if CAS failed before call
-     */
-    final void retryUpdate(long x, HashCode hc, boolean wasUncontended) {
-        int h = hc.code;
-        boolean collide = false;                // True if last slot nonempty
-        for (;;) {
-            Cell[] as; Cell a; int n; long v;
-            if ((as = cells) != null && (n = as.length) > 0) {
-                if ((a = as[(n - 1) & h]) == null) {
-                    if (busy == 0) {            // Try to attach new Cell
-                        Cell r = new Cell(x);   // Optimistically create
-                        if (busy == 0 && casBusy()) {
-                            boolean created = false;
-                            try {               // Recheck under lock
-                                Cell[] rs; int m, j;
-                                if ((rs = cells) != null &&
-                                        (m = rs.length) > 0 &&
-                                        rs[j = (m - 1) & h] == null) {
-                                    rs[j] = r;
-                                    created = true;
-                                }
-                            } finally {
-                                busy = 0;
-                            }
-                            if (created)
-                                break;
-                            continue;           // Slot is now non-empty
-                        }
-                    }
-                    collide = false;
-                }
-                else if (!wasUncontended)       // CAS already known to fail
-                    wasUncontended = true;      // Continue after rehash
-                else if (a.cas(v = a.value, fn(v, x)))
-                    break;
-                else if (n >= NCPU || cells != as)
-                    collide = false;            // At max size or stale
-                else if (!collide)
-                    collide = true;
-                else if (busy == 0 && casBusy()) {
-                    try {
-                        if (cells == as) {      // Expand table unless stale
-                            Cell[] rs = new Cell[n << 1];
-                            for (int i = 0; i < n; ++i)
-                                rs[i] = as[i];
-                            cells = rs;
-                        }
-                    } finally {
-                        busy = 0;
-                    }
-                    collide = false;
-                    continue;                   // Retry with expanded table
-                }
-                h ^= h << 13;                   // Rehash
-                h ^= h >>> 17;
-                h ^= h << 5;
-            }
-            else if (busy == 0 && cells == as && casBusy()) {
-                boolean init = false;
-                try {                           // Initialize table
-                    if (cells == as) {
-                        Cell[] rs = new Cell[2];
-                        rs[h & 1] = new Cell(x);
-                        cells = rs;
-                        init = true;
-                    }
-                } finally {
-                    busy = 0;
-                }
-                if (init)
-                    break;
-            }
-            else if (casBase(v = base, fn(v, x)))
-                break;                          // Fall back on using base
-        }
-        hc.code = h;                            // Record index for next time
-    }
-
-
-    /**
-     * Sets base and all cells to the given value.
-     */
-    final void internalReset(long initialValue) {
-        Cell[] as = cells;
-        base = initialValue;
-        if (as != null) {
-            int n = as.length;
-            for (int i = 0; i < n; ++i) {
-                Cell a = as[i];
-                if (a != null)
-                    a.value = initialValue;
-            }
-        }
-    }
-
-    // Unsafe mechanics
-    private static final sun.misc.Unsafe UNSAFE;
-    private static final long baseOffset;
-    private static final long busyOffset;
-    static {
-        try {
-            UNSAFE = getUnsafe();
-            Class<?> sk = Striped64.class;
-            baseOffset = UNSAFE.objectFieldOffset
-                    (sk.getDeclaredField("base"));
-            busyOffset = UNSAFE.objectFieldOffset
-                    (sk.getDeclaredField("busy"));
-        } catch (Exception e) {
-            throw new Error(e);
-        }
-    }
-
-    /**
-     * Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
-     * Replace with a simple call to Unsafe.getUnsafe when integrating
-     * into a jdk.
-     *
-     * @return a sun.misc.Unsafe
-     */
-    private static sun.misc.Unsafe getUnsafe() {
-        try {
-            return sun.misc.Unsafe.getUnsafe();
-        } catch (SecurityException tryReflectionInstead) {}
-        try {
-            return java.security.AccessController.doPrivileged
-                    (new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
-                        public sun.misc.Unsafe run() throws Exception {
-                            Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
-                            for (java.lang.reflect.Field f : k.getDeclaredFields()) {
-                                f.setAccessible(true);
-                                Object x = f.get(null);
-                                if (k.isInstance(x))
-                                    return k.cast(x);
-                            }
-                            throw new NoSuchFieldError("the Unsafe");
-                        }});
-        } catch (java.security.PrivilegedActionException e) {
-            throw new RuntimeException("Could not initialize intrinsics",
-                    e.getCause());
-        }
-    }
-}

common/src/test/java/io/netty/util/ThreadDeathWatcherTest.java

@@ -20,6 +20,7 @@ import org.junit.Test;
 
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
@@ -27,7 +28,7 @@ import static org.junit.Assert.*;
 public class ThreadDeathWatcherTest {
 
     @Test(timeout = 10000)
-    public void testSimple() throws Exception {
+    public void testWatch() throws Exception {
         final CountDownLatch latch = new CountDownLatch(1);
         final Thread t = new Thread() {
             @Override
@@ -70,4 +71,46 @@ public class ThreadDeathWatcherTest {
         // The task must be run on termination.
         latch.await();
     }
+
+    @Test(timeout = 10000)
+    public void testUnwatch() throws Exception {
+        final AtomicBoolean run = new AtomicBoolean();
+        final Thread t = new Thread() {
+            @Override
+            public void run() {
+                for (;;) {
+                    try {
+                        Thread.sleep(1000);
+                    } catch (InterruptedException ignore) {
+                        break;
+                    }
+                }
+            }
+        };
+
+        final Runnable task = new Runnable() {
+            @Override
+            public void run() {
+                run.set(true);
+            }
+        };
+
+        t.start();
+
+        // Watch and then unwatch.
+        ThreadDeathWatcher.watch(t, task);
+        ThreadDeathWatcher.unwatch(t, task);
+
+        // Interrupt the thread to terminate it.
+        t.interrupt();
+
+        // Wait until the thread dies.
+        t.join();
+
+        // Wait until the watcher thread terminates itself.
+        assertThat(ThreadDeathWatcher.awaitInactivity(Long.MAX_VALUE, TimeUnit.SECONDS), is(true));
+
+        // And the task should not run.
+        assertThat(run.get(), is(false));
+    }
 }

common/src/test/java/io/netty/util/concurrent/FastThreadLocalTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2014 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.util.concurrent;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.Matchers.nullValue;
+import static org.junit.Assert.*;
+
+public class FastThreadLocalTest {
+    @Before
+    public void setUp() {
+        FastThreadLocal.removeAll();
+        assertThat(FastThreadLocal.size(), is(0));
+    }
+
+    @Test(timeout = 10000)
+    public void testRemoveAll() throws Exception {
+        final AtomicBoolean removed = new AtomicBoolean();
+        final FastThreadLocal<Boolean> var = new FastThreadLocal<Boolean>() {
+            @Override
+            protected void onRemoval(Boolean value) {
+                removed.set(true);
+            }
+        };
+
+        // Initialize a thread-local variable.
+        assertThat(var.get(), is(nullValue()));
+        assertThat(FastThreadLocal.size(), is(1));
+
+        // And then remove it.
+        FastThreadLocal.removeAll();
+        assertThat(removed.get(), is(true));
+        assertThat(FastThreadLocal.size(), is(0));
+    }
+
+    @Test(timeout = 10000)
+    public void testRemoveAllFromFTLThread() throws Throwable {
+        final AtomicReference<Throwable> throwable = new AtomicReference<Throwable>();
+        final Thread thread = new FastThreadLocalThread() {
+            @Override
+            public void run() {
+                try {
+                    testRemoveAll();
+                } catch (Throwable t) {
+                    throwable.set(t);
+                }
+            }
+        };
+
+        thread.start();
+        thread.join();
+
+        Throwable t = throwable.get();
+        if (t != null) {
+            throw t;
+        }
+    }
+}

handler/src/main/java/io/netty/handler/ssl/util/FingerprintTrustManagerFactory.java

@@ -19,7 +19,7 @@ package io.netty.handler.ssl.util;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 import io.netty.util.internal.EmptyArrays;
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocal;
 
 import javax.net.ssl.ManagerFactoryParameters;
 import javax.net.ssl.TrustManager;
@@ -68,7 +68,7 @@ public final class FingerprintTrustManagerFactory extends SimpleTrustManagerFact
     private static final int SHA1_BYTE_LEN = 20;
     private static final int SHA1_HEX_LEN = SHA1_BYTE_LEN * 2;
 
-    private static final ThreadLocal<MessageDigest> tlmd = new FastThreadLocal<MessageDigest>() {
+    private static final FastThreadLocal<MessageDigest> tlmd = new FastThreadLocal<MessageDigest>() {
         @Override
         protected MessageDigest initialValue() {
             try {

handler/src/main/java/io/netty/handler/ssl/util/SimpleTrustManagerFactory.java

@@ -16,7 +16,7 @@
 
 package io.netty.handler.ssl.util;
 
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.concurrent.FastThreadLocal;
 
 import javax.net.ssl.ManagerFactoryParameters;
 import javax.net.ssl.TrustManager;
@@ -44,7 +44,7 @@ public abstract class SimpleTrustManagerFactory extends TrustManagerFactory {
      *
      * To work around this issue, we use an ugly hack which uses a {@link ThreadLocal}.
      */
-    private static final ThreadLocal<SimpleTrustManagerFactorySpi> CURRENT_SPI =
+    private static final FastThreadLocal<SimpleTrustManagerFactorySpi> CURRENT_SPI =
             new FastThreadLocal<SimpleTrustManagerFactorySpi>() {
                 @Override
                 protected SimpleTrustManagerFactorySpi initialValue() {

microbench/pom.xml

@@ -47,12 +47,12 @@
     <dependency>
       <groupId>org.openjdk.jmh</groupId>
       <artifactId>jmh-core</artifactId>
-      <version>0.8</version>
+      <version>0.9</version>
     </dependency>
     <dependency>
       <groupId>org.openjdk.jmh</groupId>
       <artifactId>jmh-generator-annprocess</artifactId>
-      <version>0.8</version>
+      <version>0.9</version>
       <scope>provided</scope>
     </dependency>
   </dependencies>

microbench/src/test/java/io/netty/microbench/buffer/ByteBufAllocatorBenchmark.java

@@ -20,7 +20,7 @@ import io.netty.buffer.ByteBufAllocator;
 import io.netty.buffer.PooledByteBufAllocator;
 import io.netty.buffer.UnpooledByteBufAllocator;
 import io.netty.microbench.util.AbstractMicrobenchmark;
-import org.openjdk.jmh.annotations.GenerateMicroBenchmark;
+import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.Param;
 
 import java.util.Random;
@@ -44,7 +44,7 @@ public class ByteBufAllocatorBenchmark extends AbstractMicrobenchmark {
     @Param({ "00000", "00256", "01024", "04096", "16384", "65536" })
     public int size;
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void unpooledHeapAllocAndFree() {
         int idx = rand.nextInt(unpooledHeapBuffers.length);
         ByteBuf oldBuf = unpooledHeapBuffers[idx];
@@ -54,7 +54,7 @@ public class ByteBufAllocatorBenchmark extends AbstractMicrobenchmark {
         unpooledHeapBuffers[idx] = unpooledAllocator.heapBuffer(size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void unpooledDirectAllocAndFree() {
         int idx = rand.nextInt(unpooledDirectBuffers.length);
         ByteBuf oldBuf = unpooledDirectBuffers[idx];
@@ -64,7 +64,7 @@ public class ByteBufAllocatorBenchmark extends AbstractMicrobenchmark {
         unpooledDirectBuffers[idx] = unpooledAllocator.directBuffer(size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void pooledHeapAllocAndFree() {
         int idx = rand.nextInt(pooledHeapBuffers.length);
         ByteBuf oldBuf = pooledHeapBuffers[idx];
@@ -74,7 +74,7 @@ public class ByteBufAllocatorBenchmark extends AbstractMicrobenchmark {
         pooledHeapBuffers[idx] = pooledAllocator.heapBuffer(size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void pooledDirectAllocAndFree() {
         int idx = rand.nextInt(pooledDirectBuffers.length);
         ByteBuf oldBuf = pooledDirectBuffers[idx];
@@ -84,13 +84,13 @@ public class ByteBufAllocatorBenchmark extends AbstractMicrobenchmark {
         pooledDirectBuffers[idx] = pooledAllocator.directBuffer(size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void defaultPooledHeapAllocAndFree() {
         ByteBuf buffer = PooledByteBufAllocator.DEFAULT.heapBuffer(size);
         buffer.release();
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void defaultPooledDirectAllocAndFree() {
         ByteBuf buffer = PooledByteBufAllocator.DEFAULT.directBuffer(size);
         buffer.release();

microbench/src/test/java/io/netty/microbench/buffer/SwappedByteBufBenchmark.java

@@ -19,7 +19,7 @@ import io.netty.buffer.ByteBuf;
 import io.netty.buffer.SwappedByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.microbench.util.AbstractMicrobenchmark;
-import org.openjdk.jmh.annotations.GenerateMicroBenchmark;
+import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.Measurement;
 import org.openjdk.jmh.annotations.Param;
 import org.openjdk.jmh.annotations.Scope;
@@ -48,32 +48,32 @@ public class SwappedByteBufBenchmark extends AbstractMicrobenchmark {
     @Param("16384")
     public int size;
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void swappedByteBufSetInt() {
         swappedByteBuf.setLong(0, size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void swappedByteBufSetShort() {
         swappedByteBuf.setShort(0, size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void swappedByteBufSetLong() {
         swappedByteBuf.setLong(0, size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void unsafeSwappedByteBufSetInt() {
         unsafeSwappedByteBuf.setInt(0, size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void unsafeSwappedByteBufSetShort() {
         unsafeSwappedByteBuf.setShort(0, size);
     }
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void unsafeSwappedByteBufSetLong() {
         unsafeSwappedByteBuf.setLong(0, size);
     }

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

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2012 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 different allocators with different allocation sizes.
+ */
+@Threads(4)
+@Measurement(iterations = 10, batchSize = 100)
+public class FastThreadLocalBenchmark 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 ++) {
+            jdkThreadLocals[i] = new ThreadLocal<Integer>() {
+                @Override
+                protected Integer initialValue() {
+                    return rand.nextInt();
+                }
+            };
+        }
+
+        for (int i = 0; i < fastThreadLocals.length; i ++) {
+            fastThreadLocals[i] = new FastThreadLocal<Integer>() {
+                @Override
+                protected Integer initialValue() {
+                    return rand.nextInt();
+                }
+            };
+        }
+    }
+
+    @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/internal/RecyclableArrayListBenchmark.java

@@ -17,7 +17,7 @@ package io.netty.microbench.internal;
 
 import io.netty.microbench.util.AbstractMicrobenchmark;
 import io.netty.util.internal.RecyclableArrayList;
-import org.openjdk.jmh.annotations.GenerateMicroBenchmark;
+import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.Measurement;
 import org.openjdk.jmh.annotations.Param;
 import org.openjdk.jmh.annotations.Threads;
@@ -32,7 +32,7 @@ public class RecyclableArrayListBenchmark extends AbstractMicrobenchmark {
     @Param({ "00000", "00256", "01024", "04096", "16384", "65536" })
     public int size;
 
-    @GenerateMicroBenchmark
+    @Benchmark
     public void recycleSameThread() {
         RecyclableArrayList list = RecyclableArrayList.newInstance(size);
         list.recycle();

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

@@ -24,7 +24,7 @@ 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.output.results.ResultFormatType;
+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;

transport/src/main/java/io/netty/channel/ChannelHandlerAdapter.java

@@ -16,9 +16,9 @@
 
 package io.netty.channel;
 
-import java.net.SocketAddress;
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.internal.InternalThreadLocalMap;
 
+import java.net.SocketAddress;
 import java.util.Map;
 import java.util.WeakHashMap;
 
@@ -27,23 +27,6 @@ import java.util.WeakHashMap;
  */
 public class ChannelHandlerAdapter implements ChannelHandler {
 
-    /**
-     * Cache the result of {@link Sharable} annotation detection to workaround a condition. We use a
-     * {@link ThreadLocal} and {@link WeakHashMap} to eliminate the volatile write/reads. Using different
-     * {@link WeakHashMap} instances per {@link Thread} is good enough for us and the number of
-     * {@link Thread}s are quite limited anyway.
-     *
-     * See <a href="See https://github.com/netty/netty/issues/2289">#2289</a>.
-     */
-    private static final ThreadLocal<Map<Class<?>, Boolean>> SHARABLE_CACHE =
-            new FastThreadLocal<Map<Class<?>, Boolean>>() {
-                @Override
-                protected Map<Class<?>, Boolean> initialValue() {
-                    // Start with small capacity to keep memory overhead as low as possible.
-                    return new WeakHashMap<Class<?>, Boolean>(4);
-                }
-            };
-
     // Not using volatile because it's used only for a sanity check.
     boolean added;
 
@@ -52,8 +35,16 @@ public class ChannelHandlerAdapter implements ChannelHandler {
      * to different {@link ChannelPipeline}s.
      */
     public boolean isSharable() {
+        /**
+         * Cache the result of {@link Sharable} annotation detection to workaround a condition. We use a
+         * {@link ThreadLocal} and {@link WeakHashMap} to eliminate the volatile write/reads. Using different
+         * {@link WeakHashMap} instances per {@link Thread} is good enough for us and the number of
+         * {@link Thread}s are quite limited anyway.
+         *
+         * See <a href="See https://github.com/netty/netty/issues/2289">#2289</a>.
+         */
         Class<?> clazz = getClass();
-        Map<Class<?>, Boolean> cache = SHARABLE_CACHE.get();
+        Map<Class<?>, Boolean> cache = InternalThreadLocalMap.get().handlerSharableCache();
         Boolean sharable = cache.get(clazz);
         if (sharable == null) {
             sharable = clazz.isAnnotationPresent(Sharable.class);

transport/src/main/java/io/netty/channel/local/LocalChannel.java

@@ -28,7 +28,7 @@ import io.netty.channel.EventLoop;
 import io.netty.channel.SingleThreadEventLoop;
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.concurrent.SingleThreadEventExecutor;
-import io.netty.util.internal.FastThreadLocal;
+import io.netty.util.internal.InternalThreadLocalMap;
 
 import java.net.SocketAddress;
 import java.nio.channels.AlreadyConnectedException;
@@ -49,12 +49,6 @@ public class LocalChannel extends AbstractChannel {
     private static final ChannelMetadata METADATA = new ChannelMetadata(false);
 
     private static final int MAX_READER_STACK_DEPTH = 8;
-    private static final ThreadLocal<Integer> READER_STACK_DEPTH = new FastThreadLocal<Integer>() {
-        @Override
-        protected Integer initialValue() {
-            return 0;
-        }
-    };
 
     private final ChannelConfig config = new DefaultChannelConfig(this);
     private final Queue<Object> inboundBuffer = new ArrayDeque<Object>();
@@ -260,9 +254,10 @@ public class LocalChannel extends AbstractChannel {
             return;
         }
 
-        final Integer stackDepth = READER_STACK_DEPTH.get();
+        final InternalThreadLocalMap threadLocals = InternalThreadLocalMap.get();
+        final Integer stackDepth = threadLocals.localChannelReaderStackDepth();
         if (stackDepth < MAX_READER_STACK_DEPTH) {
-            READER_STACK_DEPTH.set(stackDepth + 1);
+            threadLocals.setLocalChannelReaderStackDepth(stackDepth + 1);
             try {
                 for (;;) {
                     Object received = inboundBuffer.poll();
@@ -273,7 +268,7 @@ public class LocalChannel extends AbstractChannel {
                 }
                 pipeline.fireChannelReadComplete();
             } finally {
-                READER_STACK_DEPTH.set(stackDepth);
+                threadLocals.setLocalChannelReaderStackDepth(stackDepth);
             }
         } else {
             eventLoop().execute(readTask);