Tune apache performance using Apache MPM prefork module

There could be many reasons why your Apache web server is slow. One of them can be that Apache needs tuning. Tuning the Apache performance using the Apache MPM prefork module is one of them.

Tune Apache performance using MPM Prefork module

StartServers: 30% of MaxClients
MinSpareServers: 5% of MaxClients
MaxSpareServers: 10% of MaxClients
MaxRequestWorkers = MaxClients
MaxConnectionsPerChild= 10000 (To avoid problem with memory leaks in WordPress plugin themes and apps)

Edit the file with this command:

sudo nano /etc/apache2/mods-available/mpm_prefork.conf


Try these values if Apache uses 70 MB under heavy load and the server has 1 GB RAM.

<IfModule mpm_prefork_module>
 StartServers 8
 MinSpareServers 8
 MaxSpareServers 9
 MaxRequestWorkers 9
 MaxConnectionsPerChild 100

Save the changes

Ctrl+X - Y

Restart Apache

sudo service apache2 restart

It might make the server a bit slower, but there will be the most available memory, and you will not hit the roof. Hitting the limit will almost stop the server.

How to calculate the values

The initial  Ubuntu OS install uses 350 MB RAM – memory – and the server has 1 GB with memory.

Then there is half a gigabyte to run Apache clients.

You measure that each Apache instance uses 33 MB of memory. Then you would be able to run 18 servers with 650 MB available RAM. 650 MB RAM allows ten customers to download content from your site simultaneously. Often the browser uses several simultaneous instances so one user could use several Apache instances. Upgrade to 4 GB of RAM then you would have 3.5 GB available to serve your customers with Apache. 3,5 GB of available memory would suggest a “MaxClients” settings increased from ten clients to 106.


Tool nr 1 to help you determine a useful configuration

Check Apache Httpd MPM Config Limits

This Perl script compares the size of running Apache HTTP processes. This consist of the configured Prefork, worker and event MPM limits. Measured towards the server’s available memory. You might get an error message if the setting limits exceed the server’s available memory.

Check the website for the newest release.


Go to the user home folder

cd ~

Create a folder

mkdir apache-memory-test

Go to the newly created folder

cd apache-memory-test

Download the latest version. This is for version 2.5:

wget https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/check-httpd-limits/check_httpd_limits-2.5.zip

Unzip the file

unzip check_httpd_limits-2.5.zip

Make the script executable:

chmod u+x check_httpd_limits.pl

Run the script as root

sudo ./check_httpd_limits.pl

Open a bunch of web pages while you run the script many times to get an impression of the average memory consumed.


Tool number 2

Please read this tutorial about oApache” performance using optimizing MPM Prefork module


Create a folder and download and unzip the script as you did with “Tool 1”

Make the script executable

chmod u+x ap.sh

Run the script



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