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From "Xiaobing Zhou (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (AMBARI-18694) Add JVM settings of forcing garbage collections to alleviate heap consumption on DataNode
Date Tue, 25 Oct 2016 22:49:58 GMT

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

Xiaobing Zhou updated AMBARI-18694:
-----------------------------------
    Description: 
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}


> Add JVM settings of forcing garbage collections to alleviate heap consumption on DataNode
> -----------------------------------------------------------------------------------------
>
>                 Key: AMBARI-18694
>                 URL: https://issues.apache.org/jira/browse/AMBARI-18694
>             Project: Ambari
>          Issue Type: Improvement
>            Reporter: 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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