periodic threads may be released periodically, for example with waitForNextPeriod(). Is this periodic release realized by a timer, like an instance of the class PeriodicTimer?
So knowing the accuracy of a periodic timer on a system may help to estimate the accuracy of wfnp()?
Nope, waitForNextPeriod need have no connection to other timer functionality.
In Java RTS on Solaris, waitForNextPeriod is implemented through our Cyclic driver, whereas Timers are implemented using POSIX timers.
That said, these all use the Solaris cyclic subsystem at some level so the resolution is the same. For timers however there's potentially more room for latency as there is additional OS/libc code in the path.