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From GitBox <...@apache.org>
Subject [GitHub] [incubator-nemo] johnyangk commented on a change in pull request #223: [NEMO-388] Off-heap memory management (reuse ByteBuffer)
Date Thu, 25 Jul 2019 06:25:26 GMT
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_r307109913
 
 

 ##########
 File path: runtime/executor/src/main/java/org/apache/nemo/runtime/executor/data/MemoryPoolAssigner.java
 ##########
 @@ -0,0 +1,147 @@
+/*
+ * 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 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.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 all memory at the start. Memory will be occupied
and reserved from start on,
+ * which means that no OutOfMemoryError comes while requesting memory. Released memory will
return to the MemoryPool.
+ */
+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.MemoryPoolSizeMb.class) final int memorySizeMb,
+                            @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 numChunks = (long) memorySizeMb * 1024 / chunkSizeKb;
+    if (numChunks > Integer.MAX_VALUE) {
+      throw new IllegalArgumentException("Too many pages to allocate (exceeds MAX_INT)");
+    }
+    final int totalNumPages = (int) numChunks;
+    if (totalNumPages < 1) {
+      throw new IllegalArgumentException("The given amount of memory amounted to less than
one page.");
+    }
+    this.chunkSize = chunkSizeKb * 1024;
+    this.memoryPool = new MemoryPool(totalNumPages, this.chunkSize);
+  }
+
+  /**
+   * Returns a single {@link MemoryChunk} from {@link MemoryPool}.
+   *
+   * @param sequential whether the requested chunk is sequential.
+   * @return a MemoryChunk
+   * @throws MemoryAllocationException if fails to allocate MemoryChunk.
+   */
+  public MemoryChunk allocateChunk(final boolean sequential) throws MemoryAllocationException
{
+    return memoryPool.requestChunkFromPool(sequential);
+  }
+
+  /**
+   * 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 returnChunks(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;
+  }
+
+  /**
+   * Memory pool that utilizes off-heap memory.
+   * Supports pre-allocation of memory according to user specification.
+   */
+  private class MemoryPool {
+
+    private final ConcurrentLinkedQueue<ByteBuffer> pool;
 
 Review comment:
   This ConcurrentLinkedQueue seems to suggest that MemoryPool is thread-safe. 
   
   Can you annotate ThreadSafe similar to the following?
   https://github.com/apache/incubator-nemo/blob/master/runtime/master/src/main/java/org/apache/nemo/runtime/master/scheduler/PendingTaskCollectionPointer.java#L33
   
   What about MemoryPoolAssigner and MemoryChunk? Please annotate ThreadSafe and NotThreadSafe
accordingly.

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