MAPREDUCE-6923. Optimize MapReduce Shuffle I/O for small partitions. Contributed by Robert Schmidtke.

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/FadvisedFileRegion.java

@@ -111,7 +111,10 @@ public class FadvisedFileRegion extends DefaultFileRegion {
     
     long trans = actualCount;
     int readSize;
-    ByteBuffer byteBuffer = ByteBuffer.allocate(this.shuffleBufferSize);
+    ByteBuffer byteBuffer = ByteBuffer.allocate(
+        Math.min(
+            this.shuffleBufferSize,
+            trans > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) trans));
     
     while(trans > 0L &&
         (readSize = fileChannel.read(byteBuffer, this.position+position)) > 0) {