HDFS-7213. processIncrementalBlockReport performance degradation.

Contributed by Eric Payne.
(cherry picked from commit e226b5b40d716b6d363c43a8783766b72734e347)

(cherry picked from commit 946463efefec9031cacb21d5a5367acd150ef904)
(cherry picked from commit f94aa4d25c2f96faf5164e807c2c3eb031e9a1fe)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -35,6 +35,9 @@ Release 2.6.1 - UNRELEASED
 
     HDFS-8486. DN startup may cause severe data loss. (daryn via cmccabe)
 
+    HDFS-7213. processIncrementalBlockReport performance degradation.
+    (Eric Payne via kihwal)
+
     HDFS-7235. DataNode#transferBlock should report blocks that don't exist
     using reportBadBlock (yzhang via cmccabe)
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java

@@ -3105,9 +3105,11 @@ public class BlockManager {
             + " is received from " + nodeID);
       }
     }
-    blockLog.debug("*BLOCK* NameNode.processIncrementalBlockReport: " + "from "
+    if (blockLog.isDebugEnabled()) {
+      blockLog.debug("*BLOCK* NameNode.processIncrementalBlockReport: " + "from "
         + nodeID + " receiving: " + receiving + ", " + " received: " + received
         + ", " + " deleted: " + deleted);
+    }
   }
 
   /**