Performance of applications running on WildFly is a very large area as it is related to the JVM settings, Java EE API, the application server configuration, external systems and also the OS. You have to be more specific on which aspect you want to tune

We have made good experiences with FlightRecorder for load testing and verbose gc-logs plus Censum in production. It's obviously better if you have a license for FlightRecorder in production as well. Some parameters (jdbc pool size, query timeout, ...) we could only tune through enough experience from production.

For Flight Recorder there are many good tutorials on the web. Personally I like Creating Flight Recordings and Low Overhead Method Profiling with Java Mission Control by Marcus Hirt.

For Censum we run the following VM settings

-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintTenuringDistribution -XX:+PrintGCCause -XX:+PrintGCApplicationStoppedTime -Xloggc:/some/path/gc.log

and then just load the file into Censum

Flight Recorder requires at leas Java 7u40. However Java 7 is end of life in a month. Running end of life software is not an option for us as we have to be PCI-DSS compliant.