Wow, what is going on with gnu parallel? It also takes 5-7x as long as "xargs -n1 -P#" (debian stretch, i7 CPU 4C/8T). Of course, one GENERALLY runs programs

Wow, what is going on with gnu parallel? It also takes 5-7x as long as "xargs -n1 -P#" (debian stretch, i7 CPU 4C/8T). Of course, one GENERALLY runs programs like xargs or parallel where there's nontrivial work to be done by each program invoked, but 10s (my measurement) to 120s (author's) overhead on only 10,000 jobs is pretty severe -- 1 to 12ms.