HDFS-15942. Increase Quota initialization threads. Contributed by Stephen O'Donnell.

(cherry picked from commit 459df4199791a9093324e089b4a5cc880be8d6ff)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -327,7 +327,7 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final String  DFS_NAMENODE_EDITS_DIR_MINIMUM_KEY = "dfs.namenode.edits.dir.minimum";
   public static final int     DFS_NAMENODE_EDITS_DIR_MINIMUM_DEFAULT = 1;
   public static final String  DFS_NAMENODE_QUOTA_INIT_THREADS_KEY = "dfs.namenode.quota.init-threads";
-  public static final int     DFS_NAMENODE_QUOTA_INIT_THREADS_DEFAULT = 4;
+  public static final int     DFS_NAMENODE_QUOTA_INIT_THREADS_DEFAULT = 12;
 
   public static final String  DFS_NAMENODE_EDIT_LOG_AUTOROLL_MULTIPLIER_THRESHOLD = "dfs.namenode.edit.log.autoroll.multiplier.threshold";
   public static final float

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -3329,11 +3329,11 @@
 
 <property>
   <name>dfs.namenode.quota.init-threads</name>
-  <value>4</value>
+  <value>12</value>
   <description>
     The number of concurrent threads to be used in quota initialization. The
     speed of quota initialization also affects the namenode fail-over latency.
-    If the size of name space is big, try increasing this.
+    If the size of name space is big, try increasing this to 16 or higher.
   </description>
 </property>