Comment by cb321

Agreed. Adding -j1 still leaves a very large (and wildly varying actually) number of futex calls shown by strace and slows down execution by another 1.5x. So, a little boost from threads but not much. Someone more interested (than I am) in "fixing" fd should study it more. Often people do not "special case" things like "-j1" to actually be single threaded with (no MT runtime overheads) but instead "launch only 1 worker thread" and such. Might taking hacking on fd to really test what is going on.