WIP towards packed record pointers for use in optimized shuffle sort.

core/src/main/java/org/apache/spark/shuffle/unsafe/PackedRecordPointer.java

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+/*
+ * 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.spark.shuffle.unsafe;
+
+/**
+ * Wrapper around an 8-byte word that holds a 24-bit partition number and 40-bit record pointer.
+ */
+final class PackedRecordPointer {
+
+  /** Bit mask for the lower 40 bits of a long. */
+  private static final long MASK_LONG_LOWER_40_BITS = 0xFFFFFFFFFFL;
+
+  /** Bit mask for the upper 24 bits of a long */
+  private static final long MASK_LONG_UPPER_24_BITS = ~MASK_LONG_LOWER_40_BITS;
+
+  /** Bit mask for the lower 27 bits of a long. */
+  private static final long MASK_LONG_LOWER_27_BITS = 0x7FFFFFFL;
+
+  /** Bit mask for the lower 51 bits of a long. */
+  private static final long MASK_LONG_LOWER_51_BITS = 0x7FFFFFFFFFFFFL;
+
+  /** Bit mask for the upper 13 bits of a long */
+  private static final long MASK_LONG_UPPER_13_BITS = ~MASK_LONG_LOWER_51_BITS;
+
+  // TODO: this shifting is probably extremely inefficient; this is just for prototyping
+
+  /**
+   * Pack a record address and partition id into a single word.
+   *
+   * @param recordPointer a record pointer encoded by TaskMemoryManager.
+   * @param partitionId a shuffle partition id (maximum value of 2^24).
+   * @return a packed pointer that can be decoded using the {@link PackedRecordPointer} class.
+   */
+  public static long packPointer(long recordPointer, int partitionId) {
+    // Note that without word alignment we can address 2^27 bytes = 128 megabytes per page.
+    // Also note that this relies on some internals of how TaskMemoryManager encodes its addresses.
+    final int pageNumber = (int) ((recordPointer & MASK_LONG_UPPER_13_BITS) >>> 51);
+    final long compressedAddress =
+      (((long) pageNumber) << 27) | (recordPointer & MASK_LONG_LOWER_27_BITS);
+    return (((long) partitionId) << 40) | compressedAddress;
+  }
+
+  public long packedRecordPointer;
+
+  public int getPartitionId() {
+    return (int) ((packedRecordPointer & MASK_LONG_UPPER_24_BITS) >>> 40);
+  }
+
+  public long getRecordPointer() {
+    final long compressedAddress = packedRecordPointer & MASK_LONG_LOWER_40_BITS;
+    final long pageNumber = (compressedAddress << 24) & MASK_LONG_UPPER_13_BITS;
+    final long offsetInPage = compressedAddress & MASK_LONG_LOWER_27_BITS;
+    return pageNumber | offsetInPage;
+  }
+
+  public int getRecordLength() {
+    return -1; // TODO
+  }
+}

core/src/test/java/org/apache/spark/shuffle/unsafe/PackedRecordPointerSuite.java

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+/*
+ * 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.spark.shuffle.unsafe;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import org.apache.spark.unsafe.memory.ExecutorMemoryManager;
+import org.apache.spark.unsafe.memory.MemoryAllocator;
+import org.apache.spark.unsafe.memory.MemoryBlock;
+import org.apache.spark.unsafe.memory.TaskMemoryManager;
+
+public class PackedRecordPointerSuite {
+
+  @Test
+  public void heap() {
+    final TaskMemoryManager memoryManager =
+      new TaskMemoryManager(new ExecutorMemoryManager(MemoryAllocator.HEAP));
+    final MemoryBlock page0 = memoryManager.allocatePage(100);
+    final MemoryBlock page1 = memoryManager.allocatePage(100);
+    final long addressInPage1 = memoryManager.encodePageNumberAndOffset(page1, 42);
+    PackedRecordPointer packedPointerWrapper = new PackedRecordPointer();
+    packedPointerWrapper.packedRecordPointer = PackedRecordPointer.packPointer(addressInPage1, 360);
+    Assert.assertEquals(360, packedPointerWrapper.getPartitionId());
+    Assert.assertEquals(addressInPage1, packedPointerWrapper.getRecordPointer());
+    memoryManager.cleanUpAllAllocatedMemory();
+  }
+
+  @Test
+  public void offHeap() {
+    final TaskMemoryManager memoryManager =
+      new TaskMemoryManager(new ExecutorMemoryManager(MemoryAllocator.UNSAFE));
+    final MemoryBlock page0 = memoryManager.allocatePage(100);
+    final MemoryBlock page1 = memoryManager.allocatePage(100);
+    final long addressInPage1 = memoryManager.encodePageNumberAndOffset(page1, 42);
+    PackedRecordPointer packedPointerWrapper = new PackedRecordPointer();
+    packedPointerWrapper.packedRecordPointer = PackedRecordPointer.packPointer(addressInPage1, 360);
+    Assert.assertEquals(360, packedPointerWrapper.getPartitionId());
+    Assert.assertEquals(addressInPage1, packedPointerWrapper.getRecordPointer());
+    memoryManager.cleanUpAllAllocatedMemory();
+  }
+}