During performance troubleshooting on our production server, senior Apache contributors on IRC immediately flagged our MPM configuration as problematic when they saw this output:

Server MPM:     prefork

Prefork MPM creates a separate process for each request, which leads to:

• High memory consumption (PHP loaded in every process)
• Poor scalability under concurrent loads
• Inability to leverage modern threading capabilities

First, we'll install the necessary components:

sudo apt-get update
sudo apt-get install apache2-mpm-event libapache2-mod-fcgid php7.0-fpm

This installs:

• The Event MPM module
• FastCGI interface for Apache
• PHP-FPM process manager

Disable prefork and enable required modules:

sudo a2dismod mpm_prefork php7.0
sudo a2enmod mpm_event proxy_fcgi setenvif

Configure PHP-FPM pool (edit /etc/php/7.0/fpm/pool.d/www.conf):

[www]
user = www-data
group = www-data
listen = /var/run/php/php7.0-fpm.sock
listen.owner = www-data
listen.group = www-data
pm = dynamic
pm.max_children = 50
pm.start_servers = 5
pm.min_spare_servers = 5
pm.max_spare_servers = 10

Modify your virtual host to handle PHP processing via FPM:

<VirtualHost *:80>
    ServerName example.com
    DocumentRoot /var/www/html
    
    <FilesMatch \.php$>
        SetHandler "proxy:unix:/var/run/php/php7.0-fpm.sock|fcgi://localhost"
    </FilesMatch>
    
    <Directory /var/www/html>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
</VirtualHost>

After restarting services:

sudo systemctl restart apache2 php7.0-fpm

Verify with:

sudo apachectl -V | grep MPM
# Should show: Server MPM:     event

php -r 'phpinfo();' | grep 'Server API'
# Should show: Server API => FPM/FastCGI

Benchmark results from our production environment:

Metric	Prefork	Event+FPM
Memory Usage	2.1GB	850MB
Requests/sec	320	1100
Concurrent Users	150	600+

---

Many Ubuntu 16.04 servers still default to Apache's prefork MPM, which creates performance bottlenecks by:

• Loading PHP into every Apache process (even for static content)
• Preventing thread-based concurrency due to mod_php's thread-unsafe nature
• Consuming excessive memory through process duplication

Before starting, verify your current configuration:

sudo apachectl -V | grep "Server MPM"
php -v

First disable the problematic module:

sudo a2dismod php7.0
sudo apt-get remove libapache2-mod-php7.0

Install PHP-FPM and enable the proxy modules:

sudo apt-get install php7.0-fpm
sudo a2enmod proxy_fcgi setenvif
sudo a2enconf php7.0-fpm

Disable prefork and enable event:

sudo a2dismod mpm_prefork
sudo a2enmod mpm_event

Update your virtual host configuration (example for default site):

<VirtualHost *:80>
    ServerName example.com
    
    <FilesMatch \.php$>
        SetHandler "proxy:unix:/var/run/php/php7.0-fpm.sock|fcgi://localhost/"
    </FilesMatch>
    
    # Other directives...
</VirtualHost>

Check configuration and restart services:

sudo apachectl configtest
sudo systemctl restart apache2 php7.0-fpm

• Check error logs: tail -f /var/log/apache2/error.log
• Verify PHP-FPM is running: systemctl status php7.0-fpm
• Confirm MPM change: apachectl -V | grep MPM

Benchmark results from a 2GB DigitalOcean droplet:

MPM	Requests/sec	Memory Usage
Prefork	320	450MB
Event	890	210MB