Isn't nproc or nproc+1 too much? On systems with hyper-threading,
this will try using too many jobs, and might cause the system be
significantly less responsive. Maybe nproc/2 is a better default?
This is an interesting question and I suppose the answer depends on many factors. At my organization we've actually gone the other direction and default to -j (nproc * 2) on the theory that one of the two jobs is liable to be sleeping on I/O at any given time. But this is very much a YMMV area and the builtin default, if there was to be one at all, should be conservative so nproc * 2 would be a bad choice.