JIT compilation and performance
The JIT is another area that can affect the performance of your program. When deciding whether or not to use JIT compilation, you must make a balance between faster execution and increased processor usage during compilation.
The performance of short-running applications can be improved by using the -Xquickstart command-line parameter. The JIT is switched on by default, but you can use -Xint to turn it off. You also have considerable flexibility in controlling JIT processing. For more details about the JIT, see The JIT compiler and Diagnosing a JIT or AOT problem in the J9 VM reference.