Compilation parameters lead to inefficiency

var sum = 0;
var s = 1;
var iter = 100000000;

for (var i=0; i<iter; i++) {
    var e = 2*i+1;
    sum += s/e;
    s*=-1;
}

time ./d8 speed.js
real 0m6.682s
user 0m8.827s
sys 0m0.020s
time node speed.js
real 0m1.682s
user 0m0.827s
sys 0m0.020s

The gap is too big

tried on different branches. If I understand it correctly it tries to tell me that it can't read a config file, but I can't figure out which one...

Traceback (most recent call last):
File "./tools/dev/v8gen.py", line 57, in
import mb
File "/home/v8/v8/v8/tools/mb/mb.py", line 565
(self.args.config_file, e)) from e
^
SyntaxError: invalid syntax