The docs for XNIO configuration currently state that the task-keepalive (link to docs) allows you to set a time after which the threads can be expired.

However, with current implementation, this option is useless and will be disregarded.
Normally, this option would (after the given period of time) kill any extra threads in your pool above the given minimum. ATM minimal amount of threads is equal to maximum (which is in turn set by another parameter pool-size) hence no threads will ever be destroyed.
The behaviour is to be implemented in WFLY 12.

We should probably remove this options from the docs for now?
Or at least make it clear that it might/will just do nothing?