diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index 94d7e0b2b2b..c90960ec839 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -14,6 +14,9 @@ Release 2.0.5-beta - UNRELEASED
     MAPREDUCE-4892. Modify CombineFileInputFormat to not skew input slits'
     allocation on small clusters. (Bikas Saha via vinodkv)
 
+    MAPREDUCE-4990. Construct debug strings conditionally in 
+    ShuffleHandler.Shuffle#sendMapOutput(). (kkambatl via tucu)
+
   OPTIMIZATIONS
 
   BUG FIXES
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
index 56ede18706e..0beb43092a7 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
@@ -549,15 +549,19 @@ public class ShuffleHandler extends AbstractService
           ContainerLocalizer.USERCACHE + "/" + user + "/"
               + ContainerLocalizer.APPCACHE + "/"
               + ConverterUtils.toString(appID) + "/output" + "/" + mapId;
-      LOG.debug("DEBUG0 " + base);
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("DEBUG0 " + base);
+      }
       // Index file
       Path indexFileName = lDirAlloc.getLocalPathToRead(
           base + "/file.out.index", conf);
       // Map-output file
       Path mapOutputFileName = lDirAlloc.getLocalPathToRead(
           base + "/file.out", conf);
-      LOG.debug("DEBUG1 " + base + " : " + mapOutputFileName + " : " +
-          indexFileName);
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("DEBUG1 " + base + " : " + mapOutputFileName + " : "
+            + indexFileName);
+      }
       final IndexRecord info = 
         indexCache.getIndexInformation(mapId, reduce, indexFileName, user);
       final ShuffleHeader header =