2. using PortAudio adds a considerable overhead. (JACK timings and the PortAudio timings are clearly in two different leagues, separated by a factor of 1.5 up to 5). the separation is most prominent in the tests that do not involve the GUI (suggesting that the GUI overhead hides the overhead from the audio backend)
So it seems like portaudio is a bit slow to initialize on macOS. FYI, the initial pa_init() call happens in sys_get_audio_devs() via sys_set_audio_settings() in sys_arg_parse() resp. sys_loadpreferences(). I don't think this can be avoided in a reasonable way. It hasn't really been a problem in the past neither.
ad code: my gut feeling tells me that there are two promising candidates:
- the changed GUI startup protocol
- something about the audio backends
I would rule out the latter because AFAICT the audio setting and preference logic hasn't really changed between Pd 0.54 and 0.55.
Christof