The results:
Apache + mod_php: 10885 req/s, 9 ms per req.
Apache + php-fpm: 5694 req/s, 17 ms per req.
Nginx + php-fpm: 8193 req/s, 12 ms per req.
According to many benchmarks performed by others, Nginx + PHP-FPM should be much faster than Apache + mod_php, but I am seeing the opposite. What am I doing wrong?