I am running a cluster JBoss servers. Both server has 4 CPUs, dual cores. i.e. 8 logical CPUs. I want to tune the JVM setting and I found that I can use the following parameters: +UseParallelOldGC -XX:ParallelGCThreads I did some load test with different number of ParallelGCThreads. However, I was surprised from the load test result that, the Full GC time for the UseParallelOldGC is much longer than I didn't use it. E.g. A) Parallel Old GC = 7 4.1747870 secs B) Parallel Old GC = 3 4.2135090 secs C) No Parallel Old GC 2.7176180 secs Does anyone know any reason why the Parallel GC can perform poor? View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4238719#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...