johnyangk commented on a change in pull request #223: [NEMO-388] Off-heap memory management (reuse ByteBuffer) URL: https://github.com/apache/incubator-nemo/pull/223#discussion_r310469451
########## File path: runtime/executor/src/main/java/org/apache/nemo/runtime/executor/data/MemoryPoolAssigner.java ########## @@ -0,0 +1,170 @@ +/* + * 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.nemo.runtime.executor.data; + +import com.google.common.annotations.VisibleForTesting; +import net.jcip.annotations.ThreadSafe; +import org.apache.reef.tang.annotations.Parameter; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import org.apache.nemo.conf.JobConf; + +import javax.inject.Inject; +import java.nio.ByteBuffer; +import java.util.List; +import java.util.NoSuchElementException; +import java.util.concurrent.ConcurrentLinkedQueue; + +/** + * The MemoryPoolAssigner assigns the memory that Nemo uses for writing data blocks from the {@link MemoryPool}. + * Memory is represented in chunks of equal size. Consumers of off-heap memory acquire the memory by requesting + * a number of {@link MemoryChunk} they need. + * + * MemoryPoolAssigner currently supports allocation of off-heap memory only. + * + * The MemoryPoolAssigner pre-allocates user-defined amount of memory at the start. + * More memory can be allocated on-demand, but if there is no more memory to allocate, MemoryAllocationException + * is thrown and the job fails. // TODO #397: Separation of JVM heap region and off-heap memory region + */ +@ThreadSafe +public class MemoryPoolAssigner { + + private static final Logger LOG = LoggerFactory.getLogger(MemoryPoolAssigner.class.getName()); + + private final int chunkSize; + + private static final int MIN_CHUNK_SIZE_KB = 4; + + private final MemoryPool memoryPool; + + @Inject + public MemoryPoolAssigner(@Parameter(JobConf.MaxOffheapMb.class) final int maxOffheapMb, + @Parameter(JobConf.ChunkSizeKb.class) final int chunkSizeKb) { + if (chunkSizeKb < MIN_CHUNK_SIZE_KB) { + throw new IllegalArgumentException("Chunk size too small. Minimum chunk size is 4KB"); + } + final long maxNumChunks = (long) maxOffheapMb * 1024 / chunkSizeKb; + if (maxNumChunks > Integer.MAX_VALUE) { + throw new IllegalArgumentException("Too many pages to allocate (exceeds MAX_INT)"); + } + if (maxNumChunks < 1) { + throw new IllegalArgumentException("The given amount of memory amounted to less than one chunk."); + } + this.chunkSize = chunkSizeKb * 1024; + this.memoryPool = new MemoryPool((int) maxNumChunks, this.chunkSize); + } + + /** + * Returns a single {@link MemoryChunk} from {@link MemoryPool}. + * + * @return a MemoryChunk + * @throws MemoryAllocationException if fails to allocate MemoryChunk. + */ + public MemoryChunk allocateChunk() throws MemoryAllocationException { + return memoryPool.requestChunkFromPool(); + } + + /** + * Returns all the MemoryChunks in the given List of MemoryChunks. + * + * @param target the list of MemoryChunks to be returned to the memory pool. + */ + public void returnChunksToPool(final List<MemoryChunk> target) { + for (final MemoryChunk chunk: target) { + memoryPool.returnChunkToPool(chunk); + } + } + + /** + * Returns the chunk size of the memory pool. + * + * @return the chunk size in bytes. + */ + public int getChunkSize() { + return chunkSize; + } + + @VisibleForTesting + /** + * Returns the number of chunks in the pool. + */ + public int returnPoolSize() { + return memoryPool.returnPoolSize(); + } + + /** + * Memory pool that utilizes off-heap memory. + * Supports pre-allocation of memory according to user specification. + */ + @ThreadSafe + private class MemoryPool { + + private final ConcurrentLinkedQueue<ByteBuffer> pool; + private final int chunkSize; + private long maxNumChunks; + private long numChunks; + + MemoryPool(final long maxNumChunks, final int chunkSize) { + this.chunkSize = chunkSize; + this.pool = new ConcurrentLinkedQueue<>(); + this.maxNumChunks = maxNumChunks; + } + + synchronized MemoryChunk allocateNewChunk() throws MemoryAllocationException { + if (maxNumChunks <= numChunks) { + throw new MemoryAllocationException("Exceeded maximum off-heap memory"); + } + ByteBuffer memory = ByteBuffer.allocateDirect(chunkSize); + numChunks += 1; + return new MemoryChunk(memory); + } + + MemoryChunk requestChunkFromPool() throws MemoryAllocationException { + try { + if (pool.isEmpty()) { + return allocateNewChunk(); + } else { + ByteBuffer buf = pool.remove(); + return new MemoryChunk(buf); + } + } catch (final NoSuchElementException e) { + throw new MemoryAllocationException("Pool empty: Failed to retrieve MemoryChunk"); + } catch (final OutOfMemoryError e) { + throw new MemoryAllocationException("Memory allocation failed due to lack of memory"); + } + } + + /** + * Returns MemoryChunk back to memory pool. + * + * @param chunk the target MemoryChunk to be returned to the pool. + */ + void returnChunkToPool(final MemoryChunk chunk) { + ByteBuffer buf = chunk.getBuffer(); + buf.clear(); + pool.add(buf); + chunk.release(); + } + + @VisibleForTesting + int returnPoolSize() { Review comment: size()? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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