shell exec is about 30 times slower than raw exec syscall

[X512]

This is hrev57820.

Shell (Bash/Zsh etc.) execution time is very slow compared Linux/*BSD that significantly slow down Autotools based projects compilation and other tasks that heavily use shell scripts. Raw exec syscall is significantly faster (30x). I am not sure is it kernel, libroot or shell port problem, it need more investigation.

loop.sh:

#!sh

if (( $1 <= 0 ))
then
    exit
fi

exec loop.sh $(($1 - 1))

loop.c:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>


int main(int argc, char **argv)
{
    if (argc < 2)
        return 1;

    int n = atoi(argv[1]);
    if (n <= 0)
        return 0;
    
    char buf[32];
    sprintf(buf, "%d", n - 1);
    char *newArgs[3] = {argv[0], buf, NULL};
    execvp(newArgs[0], newArgs);
    
    return 0;
}

time ./loop.sh 1000:

real    0m13.775s
user    0m11.713s
sys     0m1.875s

time ./loop 1000:

real    0m0.409s
user    0m0.144s
sys     0m0.240s