[jboss-user] [Performance Tuning] - Re: Cpu 100% and GC is running

Wolf-Dieter Fink do-not-reply at jboss.com
Thu Jan 5 10:22:34 EST 2012

Wolf-Dieter Fink [http://community.jboss.org/people/wdfink] created the discussion

"Re: Cpu 100% and GC is running"

To view the discussion, visit: http://community.jboss.org/message/644864#644864

Often I see a behaviour that after reaching a threshold in memory consumption the GC become more active, this force more parallel access (because of longer duration) and this will end in more GC to handle the small rest of memory  :( 

So what you might check
- is the overall memory use increased => you will have a leak
   you might use jstat to monitor the JBoss JVM it will be not a big overhead and its possible in production
- you might have a traffic peak that end in such behaviour => check whether more memory or clustering helps
  also jstat will help

Also you should activate the GC logging (see link gc-tuning from Rado above)*:*
-verbose:+gc+ -Xloggc:/tmp/jboss_+gc+.log -XX:+PrintGCDetails ...
 The interesting log is 'Total Time where application stop' see Java +GC+ tuning
In your case I suppose a that ~1% app time and 99% of such stop time, this mean the GC must work hard to provide memory for allocation  :(

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