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https://issues.apache.org/jira/browse/CASSANDRA-504?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12768664#action_12768664
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Hudson commented on CASSANDRA-504:
----------------------------------
Integrated in Cassandra #235 (See
[http://hudson.zones.apache.org/hudson/job/Cassandra/235/])
add -XX:SurvivorRatio=128 -XX:MaxTenuringThreshold=0 to default gc options.
patch by Brandon Williams; reviewed by jbellis for
> Reduce GC overhead
> ------------------
>
> Key: CASSANDRA-504
> URL: https://issues.apache.org/jira/browse/CASSANDRA-504
> Project: Cassandra
> Issue Type: Improvement
> Environment: debian lenny amd64 Java(TM) SE Runtime Environment
> (build 1.6.0_12-b04)
> Reporter: Brandon Williams
> Assignee: Brandon Williams
> Priority: Minor
> Fix For: 0.4, 0.5
>
> Attachments: better_gc_jvm_opts.patch
>
>
> The Concurrent Mark Sweep GC is using about 30% of the cpu during inserts.
> This is not reported as GC time by jconsole, but can be observed by finding
> the thread with jstack and watching it via top. This is due to the
> CMSInitiatingOccupancyFraction=1 setting being passed to the JVM. Setting
> this to 1 is nonsensical, the default is 68.
> I tested with some runs of stress.py with 200k inserts, and removing
> CMSInitiatingOccupancyFraction causes the 30% cpu usage to disappear. ParNew
> GC time was 28-29s. Adding SurvivorRatio=128 and MaxTenuringThreshold=0
> drops the GC time to 18-20s.
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