Github user tedyu commented on a diff in the pull request:
https://github.com/apache/spark/pull/6444#discussion_r34848070
--- Diff:
core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeExternalSorter.java
---
@@ -0,0 +1,282 @@
+/*
+ * 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.util.collection.unsafe.sort;
+
+import java.io.IOException;
+import java.util.LinkedList;
+
+import com.google.common.annotations.VisibleForTesting;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.spark.SparkConf;
+import org.apache.spark.TaskContext;
+import org.apache.spark.executor.ShuffleWriteMetrics;
+import org.apache.spark.shuffle.ShuffleMemoryManager;
+import org.apache.spark.storage.BlockManager;
+import org.apache.spark.unsafe.PlatformDependent;
+import org.apache.spark.unsafe.memory.MemoryBlock;
+import org.apache.spark.unsafe.memory.TaskMemoryManager;
+import org.apache.spark.util.Utils;
+
+/**
+ * External sorter based on {@link UnsafeInMemorySorter}.
+ */
+public final class UnsafeExternalSorter {
+
+ private final Logger logger =
LoggerFactory.getLogger(UnsafeExternalSorter.class);
+
+ private static final int PAGE_SIZE = 1 << 27; // 128 megabytes
+ @VisibleForTesting
+ static final int MAX_RECORD_SIZE = PAGE_SIZE - 4;
+
+ private final PrefixComparator prefixComparator;
+ private final RecordComparator recordComparator;
+ private final int initialSize;
+ private final TaskMemoryManager memoryManager;
+ private final ShuffleMemoryManager shuffleMemoryManager;
+ private final BlockManager blockManager;
+ private final TaskContext taskContext;
+ private ShuffleWriteMetrics writeMetrics;
+
+ /** The buffer size to use when writing spills using
DiskBlockObjectWriter */
+ private final int fileBufferSizeBytes;
+
+ /**
+ * Memory pages that hold the records being sorted. The pages in this
list are freed when
+ * spilling, although in principle we could recycle these pages across
spills (on the other hand,
+ * this might not be necessary if we maintained a pool of re-usable
pages in the TaskMemoryManager
+ * itself).
+ */
+ private final LinkedList<MemoryBlock> allocatedPages = new
LinkedList<MemoryBlock>();
+
+ // These variables are reset after spilling:
+ private UnsafeInMemorySorter sorter;
+ private MemoryBlock currentPage = null;
+ private long currentPagePosition = -1;
+ private long freeSpaceInCurrentPage = 0;
+
+ private final LinkedList<UnsafeSorterSpillWriter> spillWriters = new
LinkedList<>();
+
+ public UnsafeExternalSorter(
+ TaskMemoryManager memoryManager,
+ ShuffleMemoryManager shuffleMemoryManager,
+ BlockManager blockManager,
+ TaskContext taskContext,
+ RecordComparator recordComparator,
+ PrefixComparator prefixComparator,
+ int initialSize,
+ SparkConf conf) throws IOException {
+ this.memoryManager = memoryManager;
+ this.shuffleMemoryManager = shuffleMemoryManager;
+ this.blockManager = blockManager;
+ this.taskContext = taskContext;
+ this.recordComparator = recordComparator;
+ this.prefixComparator = prefixComparator;
+ this.initialSize = initialSize;
+ // Use getSizeAsKb (not bytes) to maintain backwards compatibility for
units
+ this.fileBufferSizeBytes = (int)
conf.getSizeAsKb("spark.shuffle.file.buffer", "32k") * 1024;
+ initializeForWriting();
+ }
+
+ // TODO: metrics tracking + integration with shuffle write metrics
+ // need to connect the write metrics to task metrics so we count the
spill IO somewhere.
+
+ /**
+ * Allocates new sort data structures. Called when creating the sorter
and after each spill.
+ */
+ private void initializeForWriting() throws IOException {
+ this.writeMetrics = new ShuffleWriteMetrics();
+ // TODO: move this sizing calculation logic into a static method of
sorter:
+ final long memoryRequested = initialSize * 8L * 2;
+ final long memoryAcquired =
shuffleMemoryManager.tryToAcquire(memoryRequested);
+ if (memoryAcquired != memoryRequested) {
+ shuffleMemoryManager.release(memoryAcquired);
+ throw new IOException("Could not acquire " + memoryRequested + "
bytes of memory");
+ }
+
+ this.sorter =
+ new UnsafeInMemorySorter(memoryManager, recordComparator,
prefixComparator, initialSize);
+ }
+
+ /**
+ * Sort and spill the current records in response to memory pressure.
+ */
+ @VisibleForTesting
+ public void spill() throws IOException {
+ logger.info("Thread {} spilling sort data of {} to disk ({} {} so
far)",
+ Thread.currentThread().getId(),
+ Utils.bytesToString(getMemoryUsage()),
+ spillWriters.size(),
+ spillWriters.size() > 1 ? " times" : " time");
+
+ final UnsafeSorterSpillWriter spillWriter =
+ new UnsafeSorterSpillWriter(blockManager, fileBufferSizeBytes,
writeMetrics,
+ sorter.numRecords());
+ spillWriters.add(spillWriter);
+ final UnsafeSorterIterator sortedRecords = sorter.getSortedIterator();
+ while (sortedRecords.hasNext()) {
+ sortedRecords.loadNext();
+ final Object baseObject = sortedRecords.getBaseObject();
+ final long baseOffset = sortedRecords.getBaseOffset();
+ final int recordLength = sortedRecords.getRecordLength();
+ spillWriter.write(baseObject, baseOffset, recordLength,
sortedRecords.getKeyPrefix());
+ }
+ spillWriter.close();
+ final long sorterMemoryUsage = sorter.getMemoryUsage();
+ sorter = null;
+ shuffleMemoryManager.release(sorterMemoryUsage);
+ final long spillSize = freeMemory();
+ taskContext.taskMetrics().incMemoryBytesSpilled(spillSize);
+ initializeForWriting();
+ }
+
+ private long getMemoryUsage() {
+ return sorter.getMemoryUsage() + (allocatedPages.size() * (long)
PAGE_SIZE);
+ }
+
+ public long freeMemory() {
+ long memoryFreed = 0;
+ for (MemoryBlock block : allocatedPages) {
+ memoryManager.freePage(block);
+ shuffleMemoryManager.release(block.size());
+ memoryFreed += block.size();
+ }
+ allocatedPages.clear();
+ currentPage = null;
+ currentPagePosition = -1;
+ freeSpaceInCurrentPage = 0;
+ return memoryFreed;
+ }
+
+ /**
+ * Checks whether there is enough space to insert a new record into the
sorter.
+ *
+ * @param requiredSpace the required space in the data page, in bytes,
including space for storing
+ * the record size.
+
+ * @return true if the record can be inserted without requiring more
allocations, false otherwise.
+ */
+ private boolean haveSpaceForRecord(int requiredSpace) {
+ assert (requiredSpace > 0);
+ return (sorter.hasSpaceForAnotherRecord() && (requiredSpace <=
freeSpaceInCurrentPage));
+ }
+
+ /**
+ * Allocates more memory in order to insert an additional record. This
will request additional
+ * memory from the {@link ShuffleMemoryManager} and spill if the
requested memory can not be
+ * obtained.
+ *
+ * @param requiredSpace the required space in the data page, in bytes,
including space for storing
+ * the record size.
+ */
+ private void allocateSpaceForRecord(int requiredSpace) throws
IOException {
+ // TODO: merge these steps to first calculate total memory
requirements for this insert,
+ // then try to acquire; no point in acquiring sort buffer only to
spill due to no space in the
+ // data page.
+ if (!sorter.hasSpaceForAnotherRecord()) {
+ logger.debug("Attempting to expand sort pointer array");
+ final long oldPointerArrayMemoryUsage = sorter.getMemoryUsage();
+ final long memoryToGrowPointerArray = oldPointerArrayMemoryUsage * 2;
+ final long memoryAcquired =
shuffleMemoryManager.tryToAcquire(memoryToGrowPointerArray);
+ if (memoryAcquired < memoryToGrowPointerArray) {
+ shuffleMemoryManager.release(memoryAcquired);
+ spill();
+ } else {
+ sorter.expandPointerArray();
+ shuffleMemoryManager.release(oldPointerArrayMemoryUsage);
+ }
+ }
+
+ if (requiredSpace > freeSpaceInCurrentPage) {
+ logger.trace("Required space {} is less than free space in current
page ({})", requiredSpace,
+ freeSpaceInCurrentPage);
+ // TODO: we should track metrics on the amount of space wasted when
we roll over to a new page
+ // without using the free space at the end of the current page. We
should also do this for
+ // BytesToBytesMap.
+ if (requiredSpace > PAGE_SIZE) {
+ throw new IOException("Required space " + requiredSpace + " is
greater than page size (" +
--- End diff --
It seems this check can be lifted to beginning of method.
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