[jira] [Updated] (AMBARI-18694) DataNode JVM heap settings should include CMSInitiatingOccupancy

["Xiaobing Zhou (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AMBARI-18694?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xiaobing Zhou updated AMBARI-18694:
-----------------------------------
    Summary: DataNode JVM heap settings should include CMSInitiatingOccupancy  (was: Add JVM settings of forcing garbage collections to release DataNode heap)

> DataNode JVM heap settings should include CMSInitiatingOccupancy
> ----------------------------------------------------------------
>
>                 Key: AMBARI-18694
>                 URL: https://issues.apache.org/jira/browse/AMBARI-18694
>             Project: Ambari
>          Issue Type: Improvement
>            Reporter: Xiaobing Zhou
>            Assignee: Xiaobing Zhou
>
> As HDFS-11047 reported, DirectoryScanner does scan by deep copying FinalizedReplica. In a deployment with 500,000+ blocks, we've seen the DN heap usage being accumulated to high peaks very quickly. Deep copies of FinalizedReplica will make DN heap usage even worse if directory scans are scheduled more frequently. 
> Another factor is that huge number of ScanInfo instances corresponding to HDFS blocks are lingering in garbage to eat many heap memories until a full GC takes place.
> This proposes adding JVM settings to force GC more frequently to release DataNode heap consumed as a result of two aforementioned reasons, i.e. add the options to HADOOP_DATANODE_OPTS
> {noformat}
> -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSInitiatingOccupancyOnly -XX:ConcGCThreads=8 -XX:+UseConcMarkSweepGC
> {noformat}



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