[jboss-user] [Performance Tuning] - About the UseParallelOldGC

[cytchiu]

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? 

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