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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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 com.google.code.yanf4j.buffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.HashMap;
import java.util.Map;
import java.util.Queue;
import com.google.code.yanf4j.util.CircularQueue;
/**
* An {@link IoBufferAllocator} that caches the buffers which are likely to be
* reused during auto-expansion of the buffers.
*
* In {@link SimpleBufferAllocator}, the underlying {@link ByteBuffer} of the
* {@link IoBuffer} is reallocated on its capacity change, which means the newly
* allocated bigger {@link ByteBuffer} replaces the old small {@link ByteBuffer}
* . Consequently, the old {@link ByteBuffer} is marked for garbage collection.
*
* It's not a problem in most cases as long as the capacity change doesn't
* happen frequently. However, once it happens too often, it burdens the VM and
* the cost of filling the newly allocated {@link ByteBuffer} with {@code NUL}
* surpass the cost of accessing the cache. In 2 dual-core Opteron Italy 270
* processors, {@link CachedBufferAllocator} outperformed
* {@link SimpleBufferAllocator} in the following situation:
*
* - when a 32 bytes buffer is expanded 4 or more times,
* - when a 64 bytes buffer is expanded 4 or more times,
* - when a 128 bytes buffer is expanded 2 or more times,
* - and when a 256 bytes or bigger buffer is expanded 1 or more times.
*
* Please note the observation above is subject to change in a different
* environment.
*
* {@link CachedBufferAllocator} uses {@link ThreadLocal} to store the cached
* buffer, allocates buffers whose capacity is power of 2 only and provides
* performance advantage if {@link IoBuffer#free()} is called properly.
*
* @author The Apache MINA Project ([email protected])
* @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (Thu, 26 Jun 2008)
* $
*/
public class CachedBufferAllocator implements IoBufferAllocator {
private static final int DEFAULT_MAX_POOL_SIZE = 8;
private static final int DEFAULT_MAX_CACHED_BUFFER_SIZE = 1 << 18; // 256KB
private final int maxPoolSize;
private final int maxCachedBufferSize;
private final ThreadLocal>> heapBuffers;
private final ThreadLocal>> directBuffers;
/**
* Creates a new instance with the default parameters ({@literal
* #DEFAULT_MAX_POOL_SIZE} and {@literal #DEFAULT_MAX_CACHED_BUFFER_SIZE}).
*/
public CachedBufferAllocator() {
this(DEFAULT_MAX_POOL_SIZE, DEFAULT_MAX_CACHED_BUFFER_SIZE);
}
/**
* Creates a new instance.
*
* @param maxPoolSize
* the maximum number of buffers with the same capacity per
* thread. 0 disables this limitation.
* @param maxCachedBufferSize
* the maximum capacity of a cached buffer. A buffer whose
* capacity is bigger than this value is not pooled. 0
* disables this limitation.
*/
public CachedBufferAllocator(int maxPoolSize, int maxCachedBufferSize) {
if (maxPoolSize < 0) {
throw new IllegalArgumentException("maxPoolSize: " + maxPoolSize);
}
if (maxCachedBufferSize < 0) {
throw new IllegalArgumentException("maxCachedBufferSize: " + maxCachedBufferSize);
}
this.maxPoolSize = maxPoolSize;
this.maxCachedBufferSize = maxCachedBufferSize;
this.heapBuffers = new ThreadLocal>>() {
@Override
protected Map> initialValue() {
return newPoolMap();
}
};
this.directBuffers = new ThreadLocal>>() {
@Override
protected Map> initialValue() {
return newPoolMap();
}
};
}
/**
* Returns the maximum number of buffers with the same capacity per thread.
* 0 means 'no limitation'.
*/
public int getMaxPoolSize() {
return this.maxPoolSize;
}
/**
* Returns the maximum capacity of a cached buffer. A buffer whose capacity
* is bigger than this value is not pooled. 0 means 'no
* limitation'.
*/
public int getMaxCachedBufferSize() {
return this.maxCachedBufferSize;
}
private Map> newPoolMap() {
Map> poolMap = new HashMap>();
int poolSize = this.maxPoolSize == 0 ? DEFAULT_MAX_POOL_SIZE : this.maxPoolSize;
for (int i = 0; i < 31; i++) {
poolMap.put(1 << i, new CircularQueue(poolSize));
}
poolMap.put(0, new CircularQueue(poolSize));
poolMap.put(Integer.MAX_VALUE, new CircularQueue(poolSize));
return poolMap;
}
public IoBuffer allocate(int requestedCapacity, boolean direct) {
int actualCapacity = IoBuffer.normalizeCapacity(requestedCapacity);
IoBuffer buf;
if (this.maxCachedBufferSize != 0 && actualCapacity > this.maxCachedBufferSize) {
if (direct) {
buf = wrap(ByteBuffer.allocateDirect(actualCapacity));
}
else {
buf = wrap(ByteBuffer.allocate(actualCapacity));
}
}
else {
Queue pool;
if (direct) {
pool = this.directBuffers.get().get(actualCapacity);
}
else {
pool = this.heapBuffers.get().get(actualCapacity);
}
// Recycle if possible.
buf = pool.poll();
if (buf != null) {
buf.clear();
buf.setAutoExpand(false);
buf.order(ByteOrder.BIG_ENDIAN);
}
else {
if (direct) {
buf = wrap(ByteBuffer.allocateDirect(actualCapacity));
}
else {
buf = wrap(ByteBuffer.allocate(actualCapacity));
}
}
}
buf.limit(requestedCapacity);
return buf;
}
public ByteBuffer allocateNioBuffer(int capacity, boolean direct) {
return allocate(capacity, direct).buf();
}
public IoBuffer wrap(ByteBuffer nioBuffer) {
return new CachedBuffer(nioBuffer);
}
public void dispose() {
}
private class CachedBuffer extends AbstractIoBuffer {
private final Thread ownerThread;
private ByteBuffer buf;
protected CachedBuffer(ByteBuffer buf) {
super(CachedBufferAllocator.this, buf.capacity());
this.ownerThread = Thread.currentThread();
this.buf = buf;
buf.order(ByteOrder.BIG_ENDIAN);
}
protected CachedBuffer(CachedBuffer parent, ByteBuffer buf) {
super(parent);
this.ownerThread = Thread.currentThread();
this.buf = buf;
}
@Override
public ByteBuffer buf() {
if (this.buf == null) {
throw new IllegalStateException("Buffer has been freed already.");
}
return this.buf;
}
@Override
protected void buf(ByteBuffer buf) {
ByteBuffer oldBuf = this.buf;
this.buf = buf;
free(oldBuf);
}
@Override
protected IoBuffer duplicate0() {
return new CachedBuffer(this, buf().duplicate());
}
@Override
protected IoBuffer slice0() {
return new CachedBuffer(this, buf().slice());
}
@Override
protected IoBuffer asReadOnlyBuffer0() {
return new CachedBuffer(this, buf().asReadOnlyBuffer());
}
@Override
public byte[] array() {
return buf().array();
}
@Override
public int arrayOffset() {
return buf().arrayOffset();
}
@Override
public boolean hasArray() {
return buf().hasArray();
}
@Override
public void free() {
free(this.buf);
this.buf = null;
}
private void free(ByteBuffer oldBuf) {
if (oldBuf == null || oldBuf.capacity() > CachedBufferAllocator.this.maxCachedBufferSize || oldBuf.isReadOnly() || isDerived()
|| Thread.currentThread() != this.ownerThread) {
return;
}
// Add to the cache.
Queue pool;
if (oldBuf.isDirect()) {
pool = CachedBufferAllocator.this.directBuffers.get().get(oldBuf.capacity());
}
else {
pool = CachedBufferAllocator.this.heapBuffers.get().get(oldBuf.capacity());
}
if (pool == null) {
return;
}
// Restrict the size of the pool to prevent OOM.
if (CachedBufferAllocator.this.maxPoolSize == 0 || pool.size() < CachedBufferAllocator.this.maxPoolSize) {
pool.offer(new CachedBuffer(oldBuf));
}
}
}
}