| /* |
| * 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 org.apache.cassandra.io.util; |
| |
| import java.nio.ByteBuffer; |
| import java.util.Queue; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| import org.apache.cassandra.io.compress.BufferType; |
| import org.jctools.queues.MpmcArrayQueue; |
| |
| /** |
| * A very simple Bytebuffer pool with a fixed allocation size and a cached max allocation count. Will allow |
| * you to go past the "max", freeing all buffers allocated beyond the max buffer count on release. |
| * |
| * Has a reusable thread local ByteBuffer that users can make use of. |
| */ |
| public class SimpleCachedBufferPool |
| { |
| private final ThreadLocalByteBufferHolder bufferHolder; |
| |
| private final Queue<ByteBuffer> bufferPool; |
| |
| /** |
| * The number of buffers currently used. |
| */ |
| private AtomicInteger usedBuffers = new AtomicInteger(0); |
| |
| /** |
| * Maximum number of buffers in the compression pool. Any buffers above this count that are allocated will be cleaned |
| * upon release rather than held and re-used. |
| */ |
| private final int maxBufferPoolSize; |
| |
| /** |
| * Size of individual buffer segments on allocation. |
| */ |
| private final int bufferSize; |
| |
| private final BufferType preferredReusableBufferType; |
| |
| public SimpleCachedBufferPool(int maxBufferPoolSize, int bufferSize, BufferType preferredReusableBufferType) |
| { |
| // We want to use a bounded queue to ensure that we do not pool more buffers than maxBufferPoolSize |
| this.bufferPool = new MpmcArrayQueue<>(maxBufferPoolSize); |
| this.maxBufferPoolSize = maxBufferPoolSize; |
| this.bufferSize = bufferSize; |
| this.preferredReusableBufferType = preferredReusableBufferType; |
| this.bufferHolder = new ThreadLocalByteBufferHolder(preferredReusableBufferType); |
| } |
| |
| public ByteBuffer createBuffer() |
| { |
| usedBuffers.incrementAndGet(); |
| ByteBuffer buf = bufferPool.poll(); |
| if (buf != null) |
| { |
| buf.clear(); |
| return buf; |
| } |
| return preferredReusableBufferType.allocate(bufferSize); |
| } |
| |
| public ByteBuffer getThreadLocalReusableBuffer(int size) |
| { |
| return bufferHolder.getBuffer(size); |
| } |
| |
| public void releaseBuffer(ByteBuffer buffer) |
| { |
| assert buffer != null; |
| assert preferredReusableBufferType == BufferType.typeOf(buffer); |
| |
| usedBuffers.decrementAndGet(); |
| |
| // We use a bounded queue. By consequence if we have reached the maximum size for the buffer pool |
| // offer will return false and we know that we can simply get rid of the buffer. |
| if (!bufferPool.offer(buffer)) |
| FileUtils.clean(buffer); |
| } |
| |
| /** |
| * Empties the buffer pool. |
| */ |
| public void emptyBufferPool() |
| { |
| ByteBuffer buffer = bufferPool.poll(); |
| while(buffer != null) |
| { |
| FileUtils.clean(buffer); |
| buffer = bufferPool.poll(); |
| } |
| } |
| |
| /** |
| * Checks if the number of used buffers has exceeded the maximum number of cached buffers. |
| * |
| * @return {@code true} if the number of used buffers has exceeded the maximum number of cached buffers, |
| * {@code false} otherwise. |
| */ |
| public boolean atLimit() |
| { |
| return usedBuffers.get() >= maxBufferPoolSize; |
| } |
| |
| @Override |
| public String toString() |
| { |
| return new StringBuilder() |
| .append("SimpleBufferPool:") |
| .append(" usedBuffers:").append(usedBuffers.get()) |
| .append(", maxBufferPoolSize:").append(maxBufferPoolSize) |
| .append(", bufferSize:").append(bufferSize) |
| .toString(); |
| } |
| } |