[jboss-user] [Performance Tuning] - 100% CPU usage with lots of memory

DeanoUK do-not-reply at jboss.com
Tue Mar 18 16:48:59 EDT 2008

Hi all,

We've got an application that stores a large amount of data in-memory which is then used by a lot of users.

Subsequently we're seeing CPU usage go through the use, and every now and then hit 100% (on a quad core machine with 8GB of mem) which I believe is when the JVM tries to garbage collect. The web app can't be used until JBoss is killed and restarted.

We currently have these JVM opts:
JAVA_OPTS="$JAVA_OPTS -Xms5g -Xmx5g -XX:MaxNewSize=3g -XX:PermSize=512m -XX:MaxP
ermSize=1g -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterv
al=3600000 -Djava.awt.headless=true -d64 -verbose:gc"

Which may or may not be causing the problems - my knowledge of GC management is very limited.

We see something similar to this in the logs:

  | [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor451]
  | [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor24]
  | [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor450]
  | [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor458]
(lots more)

[Full GC 4077824K->4077824K(4660352K), 7.6307480 secs]
  | [Full GC 4077824K->4077625K(4660352K), 10.7810720 secs]
  | [Full GC 4077823K->4077823K(4660352K), 7.6245730 secs]
  | [Full GC 4077823K->4077611K(4660352K), 10.8113030 secs]
(lots more)

Any help would be much appreciated.

JBoss 4.2.1GA
SuSE Enterprise 10 SP1
Java 1.6.0_05

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