> OK, since the resolution is 1 nsec on my Ubuntu

Yeah, Linux always announce 1 nanosecond, even the real resolution is not so good:
https://lkml.org/lkml/2012/2/9/100

On Mac OS X, the resolution is also probably hardcoded to 1 nanosecond. (Python reads the resolution at runtime on Linux, Mac OS X and Windows.)

Since the granularity is back, why not using also the resolution of the selector in asyncio? :-) It would avoid useless calls for free. It can be a private attribute if you don't want to make it public. But I don't see why you would like to hide such data since time.get_clock_info(name).resolution is the same lie (at least on Linux and Mac OS X) :-) It's just a question of exposing OS data. No need to compute the effective resolution.