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From "Oleg Anastasyev (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8150) Revaluate Default JVM tuning parameters
Date Thu, 27 Nov 2014 07:55:14 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14227361#comment-14227361
] 

Oleg Anastasyev commented on CASSANDRA-8150:
--------------------------------------------

Let me add 2 -cents- GC options from our production clusters, which i believe could be useful
for all:
-XX:+CMSScavengeBeforeRemark
to reduce rescan phase even of CMSWait exceeded

-XX:+ParallelRefProcEnabled
-XX:+CMSParallelInitialMarkEnabled
to improve CMS parallelization 

-XX:CMSMaxAbortablePrecleanTime=20000

I'd also propose add -XX:+DisableExplicitGC , b/c java RMI runtime invokes a System.gc every
hour or increasing sun.rmi.dgc.server.gcInterval to infinity. 
We found, that on Sun JVMs 7 and 8 CMSWait durations are not governed by CMS when GC is initiated
by System.gc and this was the reason for most long rescan phase pauses.

> Revaluate Default JVM tuning parameters
> ---------------------------------------
>
>                 Key: CASSANDRA-8150
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8150
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Config
>            Reporter: Matt Stump
>            Assignee: Brandon Williams
>         Attachments: upload.png
>
>
> It's been found that the old twitter recommendations of 100m per core up to 800m is harmful
and should no longer be used.
> Instead the formula used should be 1/3 or 1/4 max heap with a max of 2G. 1/3 or 1/4 is
debatable and I'm open to suggestions. If I were to hazard a guess 1/3 is probably better
for releases greater than 2.1.



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