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From "Arpit Agarwal (JIRA)" <>
Subject [jira] [Updated] (AMBARI-18936) DataNode JVM heap settings should include CMSInitiatingOccupancy
Date Sat, 19 Nov 2016 20:22:58 GMT


Arpit Agarwal updated AMBARI-18936:
    Attachment: AMBARI-18936.02.patch

> DataNode JVM heap settings should include CMSInitiatingOccupancy
> ----------------------------------------------------------------
>                 Key: AMBARI-18936
>                 URL:
>             Project: Ambari
>          Issue Type: Improvement
>    Affects Versions: 2.2.2
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
>             Fix For: 2.5.0
>         Attachments: AMBARI-18936.02.patch
> This is a followup to AMBARI-18694 to fix remaining stack versions:
> ___________________________
> 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
> {noformat}

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