ashishkumar50 commented on code in PR #6455: URL: https://github.com/apache/ozone/pull/6455#discussion_r1592257051
########## hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/DirectBufferPool.java: ########## @@ -0,0 +1,103 @@ +/** + * 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.hadoop.hdds.scm.storage; + +import org.apache.hadoop.classification.VisibleForTesting; + +import java.lang.ref.WeakReference; +import java.nio.ByteBuffer; +import java.util.Queue; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentLinkedQueue; +import java.util.concurrent.ConcurrentMap; + +/** + * A simple class for pooling direct ByteBuffers. This is necessary + * because Direct Byte Buffers do not take up much space on the heap, + * and hence will not trigger GCs on their own. However, they do take + * native memory, and thus can cause high memory usage if not pooled. + * The pooled instances are referred to only via weak references, allowing + * them to be collected when a GC does run. + * + * This class only does effective pooling when many buffers will be + * allocated at the same size. There is no attempt to reuse larger + * buffers to satisfy smaller allocations. + */ +public class DirectBufferPool { + + private final ConcurrentMap<Integer, Queue<WeakReference<ByteBuffer>>> buffersBySize = + new ConcurrentHashMap<Integer, Queue<WeakReference<ByteBuffer>>>(); + + /** + * Check if in pool buffer is available for the specified size, + * If it is available return that else allocate a new buffer. + * + * @param size size. + * @return ByteBuffer. + */ + public ByteBuffer allocateBuffer(int size) { + Queue<WeakReference<ByteBuffer>> list = buffersBySize.get(size); + if (list == null) { + // Buffer is not available for the specified size + // allocate new buffer in this case + return ByteBuffer.allocateDirect(size); + } + + WeakReference<ByteBuffer> ref; + while ((ref = list.poll()) != null) { + ByteBuffer b = ref.get(); + if (b != null) { + return b; + } + } + + return ByteBuffer.allocateDirect(size); + } + + /** + * Return a buffer into the pool. After being returned, + * the buffer may be recycled, so the user must not + * continue to use it in any way. + * @param buf the buffer to return + */ + public void releaseBuffer(ByteBuffer buf) { + buf.clear(); + int size = buf.capacity(); + Queue<WeakReference<ByteBuffer>> list = buffersBySize.get(size); + if (list == null) { + list = new ConcurrentLinkedQueue<WeakReference<ByteBuffer>>(); + Queue<WeakReference<ByteBuffer>> prev = buffersBySize.putIfAbsent(size, list); + if (prev != null) { + list = prev; + } + } + list.add(new WeakReference<ByteBuffer>(buf)); + } + + /** + * Return the number of available buffers of a given size. + */ + @VisibleForTesting + int countBuffersOfSize(int size) { + Queue<WeakReference<ByteBuffer>> list = buffersBySize.get(size); + if (list == null) { + return 0; + } + return list.size(); + } Review Comment: I thought of using but `DirectBufferPool` class in hadoop-common has limited visibilty. `@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
