[jboss-user] [Performance Tuning] - jboss cpu spike - GC?

[jboden]

jboden [https://community.jboss.org/people/jboden] created the discussion

"jboss cpu spike - GC?"

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Hi,

I have a jboss 5.1 app with sun jdk 1.7.something. At night, it runs a large job and gobbles memory. The process gets to 2.5GB and never goes down, but I hear that's normal with heap space? But after a few days of this, I begin to see the cpu spike to 100% of one cpu for a few seconds, then go down. This happens every 5 seconds or so, probably GC?

Using mostly a default run.bat, I have the jvm args set to:

-Xrs -Xms256M -Xmx2048M -XX:MaxPermSize=256m -XX:+CMSClassUnloadingEnabled -XX:+UseConcMarkSweepGC 
 -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000
 -Dorg.jboss.resolver.warning=true

Should we be doing something more specific? And if the GC keeps running that often even after the thread to do the nightly job has ended, do I have a memory leak somewhere? We do sometimes run out of memory, but maybe it needs Xmx of 4gb just to finish the job. 

I'm going to up the memory anyway, but what clues do we look for to determine if there is a leak and/or better GC settings?

Thank you very much!
Jim
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