Configuring NameNode Heap Size

Okay, so as my hadoop already reach more than 6 Milion files, the current setting is not suitable for running nameNode. So need toTotal Java Heap need to  increased to 6GB.

Details can refer this arcticle : https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.6.5/bk_command-line-installation/content/configuring-namenode-heap-size.html

NameNode heap size depends on many factors, such as the number of files, the number of blocks, and the load on the system. The following table provides recommendations for NameNode heap size configuration. These settings should work for typical Hadoop clusters in which the number of blocks is very close to the number of files (generally, the average ratio of number of blocks per file in a system is 1.1 to 1.2).
Some clusters might require further tweaking of the following settings. Also, it is generally better to set the total Java heap to a higher value.

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Table 1.11. Recommended NameNode Heap Size Settings

Number of Files, in Millions	Total Java Heap (Xmx and Xms)	Young Generation Size (-XX:NewSize -XX:MaxNewSize)
< 1 million files	1126m	128m
1-5 million files	3379m	512m
5-10	5913m	768m
10-20	10982m	1280m
20-30	16332m	2048m
30-40	21401m	2560m
40-50	26752m	3072m
50-70	36889m	4352m
70-100	52659m	6144m
100-125	65612m	7680m
125-150	78566m	8960m
150-200	104473m	8960m

	Note
	Hortonworks recommends a maximum of 300 million files on the NameNode.

You should also set -XX:PermSize to 128m and -XX:MaxPermSize to 256m.
Following are the recommended settings for HADOOP_NAMENODE_OPTS in the hadoop-env.sh file (replacing the ##### placeholder for -XX:NewSize, -XX:MaxNewSize, -Xms, and -Xmx with the recommended values from the table):

-server -XX:ParallelGCThreads=8 -XX:+UseConcMarkSweepGC -XX:ErrorFile=/var/log/hadoop/$USER/hs_err_pid%p.log -XX:NewSize=##### -XX:MaxNewSize=##### -Xms##### -Xmx##### -XX:PermSize=128m -XX:MaxPermSize=256m -Xloggc:/var/log/hadoop/$USER/gc.log-`date +'%Y%m%d%H%M'` -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Dhadoop.security.logger=INFO,DRFAS -Dhdfs.audit.logger=INFO,DRFAAUDIT ${HADOOP_NAMENODE_OPTS}

If the cluster uses a secondary NameNode, you should also set HADOOP_SECONDARYNAMENODE_OPTS to HADOOP_NAMENODE_OPTS in the hadoop-env.sh file:

HADOOP_SECONDARYNAMENODE_OPTS=$HADOOP_NAMENODE_OPTS

Another useful HADOOP_NAMENODE_OPTS setting is -XX:+HeapDumpOnOutOfMemoryError. This option specifies that a heap dump should be executed when an out-of-memory error occurs. You should also use -XX:HeapDumpPath to specify the location for the heap dump file:

-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=./etc/heapdump.hprof