[SPARK-17839][CORE] Use Nio's directbuffer instead of BufferedInputStream in order to avoid additional copy from os buffer cache to user buffer

## What changes were proposed in this pull request?

Currently we use BufferedInputStream to read the shuffle file which copies the file content from os buffer cache to the user buffer. This adds additional latency in reading the spill files. We made a change to use java nio's direct buffer to read the spill files and for certain pipelines spilling significant amount of data, we see up to 7% speedup for the entire pipeline.

## How was this patch tested?
Tested by running the job in the cluster and observed up to 7% speedup.

Author: Sital Kedia <skedia@fb.com>

Closes #15408 from sitalkedia/skedia/nio_spill_read.

1 files changed, 135 insertions, 0 deletions

diff --git a/core/src/test/java/org/apache/spark/io/NioBufferedFileInputStreamSuite.java b/core/src/test/java/org/apache/spark/io/NioBufferedFileInputStreamSuite.java
new file mode 100644
index 0000000000..2c1a34a607
--- /dev/null
+++ b/core/src/test/java/org/apache/spark/io/NioBufferedFileInputStreamSuite.java
@@ -0,0 +1,135 @@
+/*
+ * 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.io;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.lang3.RandomUtils;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests functionality of {@link NioBufferedFileInputStream}
+ */
+public class NioBufferedFileInputStreamSuite {
+
+  private byte[] randomBytes;
+
+  private File inputFile;
+
+  @Before
+  public void setUp() throws IOException {
+    // Create a byte array of size 2 MB with random bytes
+    randomBytes =  RandomUtils.nextBytes(2 * 1024 * 1024);
+    inputFile = File.createTempFile("temp-file", ".tmp");
+    FileUtils.writeByteArrayToFile(inputFile, randomBytes);
+  }
+
+  @After
+  public void tearDown() {
+    inputFile.delete();
+  }
+
+  @Test
+  public void testReadOneByte() throws IOException {
+    InputStream inputStream = new NioBufferedFileInputStream(inputFile);
+    for (int i = 0; i < randomBytes.length; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+  }
+
+  @Test
+  public void testReadMultipleBytes() throws IOException {
+    InputStream inputStream = new NioBufferedFileInputStream(inputFile);
+    byte[] readBytes = new byte[8 * 1024];
+    int i = 0;
+    while (i < randomBytes.length) {
+      int read = inputStream.read(readBytes, 0, 8 * 1024);
+      for (int j = 0; j < read; j++) {
+        assertEquals(randomBytes[i], readBytes[j]);
+        i++;
+      }
+    }
+  }
+
+  @Test
+  public void testBytesSkipped() throws IOException {
+    InputStream inputStream = new NioBufferedFileInputStream(inputFile);
+    assertEquals(1024, inputStream.skip(1024));
+    for (int i = 1024; i < randomBytes.length; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+  }
+
+  @Test
+  public void testBytesSkippedAfterRead() throws IOException {
+    InputStream inputStream = new NioBufferedFileInputStream(inputFile);
+    for (int i = 0; i < 1024; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+    assertEquals(1024, inputStream.skip(1024));
+    for (int i = 2048; i < randomBytes.length; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+  }
+
+  @Test
+  public void testNegativeBytesSkippedAfterRead() throws IOException {
+    InputStream inputStream = new NioBufferedFileInputStream(inputFile);
+    for (int i = 0; i < 1024; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+    // Skipping negative bytes should essential be a no-op
+    assertEquals(0, inputStream.skip(-1));
+    assertEquals(0, inputStream.skip(-1024));
+    assertEquals(0, inputStream.skip(Long.MIN_VALUE));
+    assertEquals(1024, inputStream.skip(1024));
+    for (int i = 2048; i < randomBytes.length; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+  }
+
+  @Test
+  public void testSkipFromFileChannel() throws IOException {
+    InputStream inputStream = new NioBufferedFileInputStream(inputFile, 10);
+    // Since the buffer is smaller than the skipped bytes, this will guarantee
+    // we skip from underlying file channel.
+    assertEquals(1024, inputStream.skip(1024));
+    for (int i = 1024; i < 2048; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+    assertEquals(256, inputStream.skip(256));
+    assertEquals(256, inputStream.skip(256));
+    assertEquals(512, inputStream.skip(512));
+    for (int i = 3072; i < randomBytes.length; i++) {
+      assertEquals(randomBytes[i], (byte) inputStream.read());
+    }
+  }
+
+  @Test
+  public void testBytesSkippedAfterEOF() throws IOException {
+    InputStream inputStream = new NioBufferedFileInputStream(inputFile);
+    assertEquals(randomBytes.length, inputStream.skip(randomBytes.length + 1));
+    assertEquals(-1, inputStream.read());
+  }
+}