Added comment.

apache · Jan 18, 2015 · beed86d · beed86d
1 parent bde6512
commit beed86d
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/core/src/main/scala/org/apache/spark/serializer/SerializationDebugger.scala b/core/src/main/scala/org/apache/spark/serializer/SerializationDebugger.scala
@@ -31,6 +31,9 @@ object SerializationDebugger {
   /**
    * Write an object to the [[ObjectOutputStream]]. If a NotSerializableException is encountered,
    * use our debug stream to capture the serialization stack leading to the problematic object.
+   *
+   * The debug stream is more expensive to write to, so we only write to it when we encounter
+   * an exception. This ensures no performance impact.
    */
   def writeObject(out: ObjectOutputStream, obj: Any): Unit = {
     try {