diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 3ff09794d1a..e57fa487009 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -1940,6 +1940,8 @@ Release 0.23.5 - UNRELEASED
 
   OPTIMIZATIONS
 
+    HDFS-4075. Reduce recommissioning overhead (Kihwal Lee via daryn)
+
   BUG FIXES
 
     HDFS-3829. TestHftpURLTimeouts fails intermittently with JDK7  (Trevor
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
index b2f344d17a0..3a971fbf0d4 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
@@ -2696,6 +2696,7 @@ assert storedBlock.findDatanode(dn) < 0 : "Block " + block
   void processOverReplicatedBlocksOnReCommission(
       final DatanodeDescriptor srcNode) {
     final Iterator<? extends Block> it = srcNode.getBlockIterator();
+    int numOverReplicated = 0;
     while(it.hasNext()) {
       final Block block = it.next();
       BlockCollection bc = blocksMap.getBlockCollection(block);
@@ -2705,8 +2706,11 @@ assert storedBlock.findDatanode(dn) < 0 : "Block " + block
       if (numCurrentReplica > expectedReplication) {
         // over-replicated block 
         processOverReplicatedBlock(block, expectedReplication, null, null);
+        numOverReplicated++;
       }
     }
+    LOG.info("Invalidated " + numOverReplicated + " over-replicated blocks on " +
+        srcNode + " during recommissioning");
   }
 
   /**
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
index a8d31392156..23013d7d911 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
@@ -608,7 +608,11 @@ public class DatanodeManager {
     if (node.isDecommissionInProgress() || node.isDecommissioned()) {
       LOG.info("Stop Decommissioning " + node);
       heartbeatManager.stopDecommission(node);
-      blockManager.processOverReplicatedBlocksOnReCommission(node);
+      // Over-replicated blocks will be detected and processed when 
+      // the dead node comes back and send in its full block report.
+      if (node.isAlive) {
+        blockManager.processOverReplicatedBlocksOnReCommission(node);
+      }
     }
   }