Meaning of new i/o latency indicator

Getting Stuff Done How do I .... ?
#1

Good afternoon
What does the i/o latency indicator at the top of the edit window tell us?
I set my usb interface up with a buffer of 960 and 3 periods and this tells me 20ms latency
However in my current session the displayed i/o latency value is 218ms
Is this good or bad?
Many thanks

#2

It shows the complete round-trip latency incl. calibrated systemic latency and plugin delay (if any).

20ms buffer-size. The nominal latency here would be 960 * (3 + 1) / 48kHz = 80ms.
That does not include systemic latency (kernel, USB, driver buffers) nor plugin delays (lookahead).

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PS. It’s not new, it has been available as toolbar item since Ardour 6. In Ardour 9 it was moved to the status bar.

#3

Many thanks for the thorough explanation Robin