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Subject [GitHub] [incubator-nemo] johnyangk commented on a change in pull request #223: [NEMO-388] Off-heap memory management (reuse ByteBuffer)
Date Tue, 23 Jul 2019 07:29:37 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_r306162724
 
 

 ##########
 File path: runtime/executor/src/main/java/org/apache/nemo/runtime/executor/data/MemoryChunk.java
 ##########
 @@ -0,0 +1,811 @@
+/*
+ * 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 java.lang.reflect.Field;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+
+/**
+ * This class represents chunk of memory residing in off-heap region
+ * managed by {@link MemoryPoolAssigner}, which is backed by {@link ByteBuffer}.
+ */
+public class MemoryChunk {
+
+  @SuppressWarnings("restriction")
+  protected static final sun.misc.Unsafe UNSAFE = getUnsafe();
+  @SuppressWarnings("restriction")
+  protected static final long BYTE_ARRAY_BASE_OFFSET = UNSAFE.arrayBaseOffset(byte[].class);
+  private static final boolean LITTLE_ENDIAN = (ByteOrder.nativeOrder() == ByteOrder.LITTLE_ENDIAN);
+  private final ByteBuffer buffer;
+  private long address;
+  private final long addressLimit;
+  private boolean isFree;
+  private final int size;
+  private final boolean sequential;
+
+  /**
+   * Creates a new memory chunk that represents the off-heap memory at the absolute address.
+   * This class can be created in two modes: sequential access mode or random access mode.
+   * Sequential access mode supports convenient sequential access of {@link ByteBuffer}.
+   * Random access mode supports random access and manipulation of the data in the {@code
ByteBuffer} using UNSAFE.
+   * No automatic tracking of position, limit, capacity, etc. of {@code ByteBuffer} for random
access mode.
+   *
+   * @param offHeapAddress the address of the off-heap memory, {@link ByteBuffer}, of this
MemoryChunk
+   * @param buffer         the off-heap memory of this MemoryChunk
+   * @param sequential     whether this MemoryChunk is in sequential mode or not.
+   */
+  MemoryChunk(final long offHeapAddress, final ByteBuffer buffer, final boolean sequential)
{
+    if (offHeapAddress <= 0) {
+      throw new IllegalArgumentException("negative pointer or size");
+    }
+    if (offHeapAddress >= Long.MAX_VALUE - Integer.MAX_VALUE) {
+      throw new IllegalArgumentException("MemoryChunk initialized with too large address");
+    }
+    this.buffer = buffer;
+    this.size = buffer.capacity();
+    this.address = offHeapAddress;
+    this.addressLimit = this.address + this.size;
+    this.isFree = false;
+    this.sequential = sequential;
+  }
+
+  /**
+   * Creates a new memory chunk that represents the off-heap memory at the absolute address.
+   *
+   * @param buffer  the off-heap memory of this MemoryChunk
+   * @param sequential  whether this MemoryChunk is in sequential mode or not.
+   */
+  MemoryChunk(final ByteBuffer buffer, final boolean sequential) {
+    this(getAddress(buffer), buffer, sequential);
+  }
+
+  /**
+   * Gets the {@link ByteBuffer} from this MemoryChunk.
+   *
+   * @return  {@link ByteBuffer}
+   */
+  public ByteBuffer getBuffer() {
+    return buffer;
+  }
+
+  /**
+   * Returns the off-heap memory address of this MemoryChunk.
+   *
+   * @return absolute memory address outside the heap
+   */
+  public long getAddress() {
 
 Review comment:
   Remove this unused method.

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