[jira] [Commented] (CASSANDRA-8932) Update default Garbage Collector GC on cassandra ps: Use G1GC instead of CMS

["Rekha Joshi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-8932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14352269#comment-14352269 ] 

Rekha Joshi commented on CASSANDRA-8932:
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[~snazy] great.thanks for your quick note.

> Update default Garbage Collector GC on cassandra ps: Use G1GC instead of CMS 
> -----------------------------------------------------------------------------
>
>                 Key: CASSANDRA-8932
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8932
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Rekha Joshi
>            Assignee: Rekha Joshi
>
> On Cassandra 2.0.8.39/DSE 4.5.1/Java HotSpot(TM) 64-Bit Server VM/1.7.0_67 encountered long running GC before dse was shutdown.
> This was a ring of 6 nodes, and no unexpected load/processes were run.The error log attached.
> Suspect was that it has hit hotspot/java GC issue.But in this case the class unloading is enabled.
> JVM_OPTS="$JVM_OPTS -XX:+CMSClassUnloadingEnabled”
> XX:CMSInitiatingOccupancyFraction=75
> On a general note, what would make things better is to make G1GC as default garbage collector (for cassandra running > java 7 update 9) instead of CMS., as G1GC is far better.For eg: -XX:+UseG1GC -XX:MaxGCPauseMillis=50
> http://www.oracle.com/technetwork/tutorials/tutorials-1876574.html
> Perhaps also can be looked if 1.when CPU utilization kicks or heap size leak/long running GC is sensed, the nodetool -h localhost flush can auto kick in?
> 2. force log the query when long running GC kicks in to make debuging easier.



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