@return the maximum delay reported by the backend since startup or reset. When compared to the period size in usecs, this can be used to estimate the ideal period size for a given setup.
@return the delay in microseconds due to the most recent XRUN occurrence. This probably only makes sense when called from a @ref JackXRunCallback defined using jack_set_xrun_callback().
Reset the maximum delay counter. This would be useful to estimate the effect that a change to the configuration of a running system (e.g. toggling kernel preemption) has on the delay experienced by JACK, without having to restart the JACK engine.