You could write a non-shell launcher using fork+exec+wait and present the results with finer granularity than time(1). There may be something adequate available off-the-shelf but I’m not familiar with it.
$ git clone https://github.com/jart/cosmopolitan && cd cosmopolitan
$ make -j8 o//examples/rusage.com o//examples/hello.com
$ o//examples/rusage.com o//examples/hello.com
hello world 123
RL: took 90µs wall time
RL: ballooned to 108kb in size
RL: needed 106µs cpu (0% kernel)
RL: caused 13 page faults (100% memcpy)
int ws, pid;
CHECK_NE(-1, (pid = fork()));
if (!pid) {
execve("ape.com", (char *const[]){"ape.com", 0}, environ);
perror("execve");
_Exit(127);
}
CHECK_EQ(pid, wait(&ws));
CHECK_TRUE(WIFEXITED(ws));
CHECK_EQ(0, WEXITSTATUS(ws));
FORK+EXEC+EXIT+WAIT │ APE │ APE-LOADER │ BINFMT_MISC
───────────────────────────────────────────────────────────────
fork() + execve() │ 55µs │ 66µs │ 56µs
vfork() + execve() │ 25µs │ 446µs │ 35µs
/bin/sh -c ./ape (1st) │ 485µs │ 457µs │ 170µs
/bin/sh -c ./ape (avg) │ 148µs │ 466µs │ 159µsThen for my musl-gcc hello world, I did, "for i in {1..10}; do o//examples/rusage.com ../hello" and the lowest wall time I got was 120us. But most of the runs were closer to 350us.
So, my attempt to answer your, "Why does hello world take 1.8ms to run?" question is: a) they timed it with "time" which measures lots of overhead, b) there's something wrong with their setup that means they are mostly timing the time taken for a CPU core to wake up.