IBM continues to improve the performance of Java on the mainframe. To show this I’ve taken a snapshot of the performance improvements during the latest Java releases. The operating system was a SLES 12 SP1 and this was run on a z13 LPAR with 6 cores and SMT enabled.
As you can see you there is a solid 33% percent improvement going from the first Java 7 version to the latest Java 8 SR3 FP10 version.
So the first recommendation when you are having Java performance problems with Linux on System z is to try a more advanced Java version.