The implementation for honoring the system property "sun.nio.ch.bugLevel" uses the same pattern as was used for "sun.nio.cs.bugLevel". The method sun.nio.ch.Util.atBugLevel() returns a value that is stored in a volatile field. The synchronization efforts that "volatile" implies can significantly harm performance on some platforms.
JDK-8182743, the handling for "sun.nio.cs.bugLevel" has been removed completely. Although "sun.nio.ch.bugLevel" is probably not queried at performance relevant places, such as the former was, the aim of this bug is to try to remove this as well or at least get rid of the volatile.