But the module does not use any threads, and use blocking IO calls.
So all vibe.d file-io is in fact blocking? What do I miss?The old Posix implementation indeed just used blocking calls (except for the win32 driver). However, it will be deprecated very soon, and the replacement, vibe-core, already uses actual thread-backed I/O for non-Windows systems through the "eventcore" library: https://github.com/vibe-d/eventcore/blob/master/source/eventcore/drivers/threadedfile.d
I do not really get why you use threads. Why don't you simply use libevent2 for that (that is the whole purpose of having libevent2)?