JVM job for Tomcat taking lots and lots of CPU

"James H. H. Lampert" <jamesl-6/ELSmrcqeUu8xhjR5IN5AC/[email protected]>
Newsgroups gmane.comp.lang.as400.java
Message-ID <[email protected]>
Ladies and Gentlemen:

We have a customer installation in which the JVM job for our Tomcat 
server is frequently using massive amounts of CPU.

It is running in a subsystem with a private pool The private pool (5) is 
currently showing fewer page-faults in WRKSYSSTS than the base pool.
> 1  3052.92 1789.92 +++++     .0     .0     .0       .0
> 2 47586.35  264.65   621   11.2  979.9  377.4   1224.3
> 3   649.51     .00    13     .0     .0     .0       .0
> 4  6495.19     .00  1215     .1     .8     .8      1.6
> 5  7168.00    2.32   500     .0     .0    3.3      6.2

GC information on the JVM job shows:
> Garbage collected heap:                                    
>   Initial heap size  . . . . . . . . . :          3096.000M
>   Maximum heap size  . . . . . . . . . :          5120.000M
>   Current heap size  . . . . . . . . . :          4458.562M
>   Heap in use  . . . . . . . . . . . . :          1907.673M
> Other memory:                                              
>   Internal (break) memory size . . . . :           504.982M
>   JIT memory size  . . . . . . . . . . :            74.000M
>   Shared classes memory size . . . . . :             0.000M
> General GC information:                                    
>   Current GC cycle . . . . . . . . . . :               2184
>   GC policy type . . . . . . . . . . . :             GENCON
>   Current GC cycle time  . . . . . . . :                552
>   Accumulated GC time  . . . . . . . . :            5108241

The job is currently running in Java 7, on a V7R3 box, with -Xms3096m 
and -Xmx5120m JVM arguments.

Would switching to Java 8 help? What are the maximum meaningful -Xms and 
-Xmx values for Java 7 and Java 8, respectively?
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