How to reduce Apache memory usage on a VPS by tuning the prefork MPM settings, using the apachebuddy.pl script to analyze process consumption and calculate optimal MaxClients values.

How to limit processes amount

First you need to download a little script I found called apachebuddy.pl by Gustav Maskowitz. Running this script shows you how many processes are running and how much memory the average process consumes.

Gathering information… We are checking the service running on port 80 The process listening on port 80 is /usr/sbin/httpd The process running on port 80 is Apache/2.2.15 (Unix) Apache has been running 0d 0h 14m 20s The full path to the Apache config file is: /etc/httpd/conf/httpd.conf Apache is using prefork model

Examining your Apache configuration… Apache runs as apache Your max clients setting is 8

Analyzing memory use… Your server has 490 MB of memory The largest apache process is using 43.35 MB of memory The smallest apache process is using 8.91 MB of memory The average apache process is using 31.87 MB of memory Going by the average Apache process, Apache can potentially use 254.97 MB RAM (52.04 % of available RAM) Going by the largest Apache process, Apache can potentially use 346.81 MB RAM (70.78 % of available RAM)

Generating reports… ### GENERAL REPORT ###

Settings considered for this report:

Your server’s physical RAM: 490MB Apache’s MaxClients directive: 8 Apache MPM Model: prefork Largest Apache process (by memory): 43.35MB Your MaxClients setting is within an acceptable range. Max potential memory usage: 346.8 MB

Percentage of RAM allocated to Apache [ OK ]

Using this data I’ve calculated how many processes I can run. These are the new settings I have set in my httpd.conf:

# prefork MPM # StartServers: number of server processes to start # MinSpareServers: minimum number of server processes which are kept spare # MaxSpareServers: maximum number of server processes which are kept spare # ServerLimit: maximum value for MaxClients for the lifetime of the server # MaxClients: maximum number of server processes allowed to start # MaxRequestsPerChild: maximum number of requests a server process serves

StartServers 2 MinSpareServers 1 MaxSpareServers 3 ServerLimit 8 MaxClients 8 MaxRequestsPerChild 1000

You need to save at least 128MB for your operating system

Don’t forget to tweak MySQL if you are using it