How to change default mpm module of apache in Centos

In the RedHat-based Linux distributions, Apache webserver is configured to run with the prefork module by default; however, you can switch it to "worker" if you decide that this would suit your needs better. Usually, it is sufficient to uncomment this directive in the /etc/sysconfig/httpd file:

# grep HTTPD= /etc/sysconfig/httpd
#HTTPD=/usr/sbin/httpd.worker

and restart Apache

/etc/init.d/httpd restart