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Issue about datanode memory usage with Hadoop?

+1 vote
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I have a job running very slowly, when I examine cluster, I find my hdfs user using 170m swap though top command, thats user run datanode daemon, ps output show following info, there are two -Xmx value, and i do not know which value is the real ,1000m or 10240m

# ps -ef|grep 2853
root      2095  1937  0 15:06 pts/4    00:00:00 grep 2853
hdfs      2853     1  5 Nov07 ?        1-22:34:22 /usr/java/jdk1.7.0_45/bin/java -Dproc_datanode -Xmx1000m -Dhadoop.log.dir=/var/log/hadoop-hdfs -Dhadoop.log.file=hadoop-hdfs-datanode-ch14.log -Dhadoop.home.dir=/usr/lib/hadoop -Dhadoop.id.str=hdfs -Dhadoop.root.logger=INFO,RFA -Djava.library.path=/usr/lib/hadoop/lib/native -Dhadoop.policy.file=hadoop-policy.xml -Djava.net.preferIPv4Stack=true -server -Xmx10240m -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -Xloggc:/var/log/hadoop-hdfs/gc-ch14-datanode.log -Dhadoop.security.logger=INFO,RFAS org.apache.hadoop.hdfs.server.datanode.DataNode
posted Dec 10, 2013 by Garima Jain

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it depends. I think Oracle JDK applies the rightmost. Check this if it is helpful  http://stackoverflow.com/questions/2740725/duplicated-java-runtime-options-what-is-the-order-of-preference

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We've tried to specify JVM flags during hadoop daemon's starts,

e.g. export HADOOP_NAMENODE_OPTS="-XX:UseNUMA -Dcom.sun.management.jmxremote $HADOOP_NAMENODE_OPTS",  
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