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The (dv) Dedicated-Virtual 4.0 server is a fairly forgiving environment for Apache. The prefork settings included in httpd.conf follow a standard linear progression with regards to available RAM and will normally produce suitable results for users. However, servers with heavy resource usage may see improved performance by scaling these settings more conservatively. Additionally, the default Apache build includes a number of modules that are most likely not in use. Removing these from the configuration will free up RAM to be available elsewhere on the server.

The information/suggestions in this article are not steps that need to be done in order. Each set of commands will make changes that may (or may not!) improve performance in a different way. However, before proceeding, the cardinal rule must first be taken care of: make a backup!

cp -p /etc/httpd/conf/httpd.conf /etc/httpd/conf/httpd.conf-backupMIB

This command can be used to lessen the amount of resources that Apache can "run away" with at any one time. For busier servers, this allows you to observe its memory levels change, or if other processes immediately start to make use of the memory which is now available. From there, additional troubleshooting would be necessary to determine if those other processes were problematic in their own right or not.

First, a few variable calculations are required based on current server beancounters. The following commands take the available information from /proc/user_beancounters and returns a number. If your (dv) has 512M RAM, this number is 1; for 1G RAM, it is 2; for 2G RAM, it is 3; so on and so forth:

ramCount=`awk 'match($0,/vmguar/) {print $4}' /proc/user_beancounters`

ramBase=-16 && for ((;ramCount>1;ramBase++)); do ramCount=$((ramCount/2)); done

With this information, adjustments can now be made to the prefork settings in httpd.conf. The following is a single command:

perl -0 -p -i -e 's/(\<IfModule\sprefork\.c\>(\n|[^\n])*?StartServers\s*?)\s\d+/\1\ '"$ramBase"'/;' \
-e 's/(\<IfModule\sprefork\.c\>(\n|[^\n])*?MinSpareServers\s*?)\s\d+/\1\ '"$ramBase"'/;' \
-e 's/(\<IfModule\sprefork\.c\>(\n|[^\n])*?MaxSpareServers\s*?)\s\d+/\1\ '"$(($ramBase*2 + 1))"'/;' \
-e 's/(\<IfModule\sprefork\.c\>(\n|[^\n])*?ServerLimit\s*?)\s\d+/\1\ '"$(( 50 + (($ramBase**2)*10) + (($ramBase-2)*10) ))"'/;' \
-e 's/(\<IfModule\sprefork\.c\>(\n|[^\n])*?MaxClients\s*?)\s\d+/\1\ '"$(( 50 + (($ramBase**2)*10) + (($ramBase-2)*10) ))"'/;' \
-e 's/(\<IfModule\sprefork\.c\>(\n|[^\n])*?MaxRequestsPerChild\s*?)\s\d+/\1\ '"$(( 2048 + ($ramBase*256) ))"'/;' /etc/httpd/conf/httpd.conf

Again, these changes are only suggested settings. Particular users may find better results comparing and contrasting the original backup file with the values that this provides and creating customized settings.

mv /etc/httpd/conf.d/perl.conf /etc/httpd/conf.d/perl.conf-disabled

mv /etc/httpd/conf.d/python.conf /etc/httpd/conf.d/python.conf-disabled

This command will lessen the resources Apache is claiming each time it needs to spawn a process. Each module loaded requires a slightly bulkier process, which means a higher idle RAM usage. For servers using a large number of Apache processes without any need for these modules, this will free up this RAM for use elsewhere.

The following command is a single command. If you see a module listed that you do not want disabled, simply remove that line from the command before executing it. If you need to re-enable a module afterward, you can manually edit /etc/httpd/conf/httpd.conf and remove the comment (# symbol) in any LoadModule directive that needs to take effect.

perl -0 -p -i -e 's/\#?(LoadModule\ authn_alias_module\ modules\/mod_authn_alias\.so)/#\1/;' \
-e 's/\#?(LoadModule\ authn_anon_module\ modules\/mod_authn_anon\.so)/#\1/;' \
-e 's/\#?(LoadModule\ authn_dbm_module\ modules\/mod_authn_dbm\.so)/#\1/;' \
-e 's/\#?(LoadModule\ authz_owner_module\ modules\/mod_authz_owner\.so)/#\1/;' \
-e 's/\#?(LoadModule\ authz_dbm_module\ modules\/mod_authz_dbm\.so)/#\1/;' \
-e 's/\#?(LoadModule\ ldap_module\ modules\/mod_ldap\.so)/#\1/;' \
-e 's/\#?(LoadModule\ authnz_ldap_module\ modules\/mod_authnz_ldap\.so)/#\1/;' \
-e 's/\#?(LoadModule\ ext_filter_module\ modules\/mod_ext_filter\.so)/#\1/;' \
-e 's/\#?(LoadModule\ usertrack_module\ modules\/mod_usertrack\.so)/#\1/;' \
-e 's/\#?(LoadModule\ dav_module\ modules\/mod_dav\.so)/#\1/;' \
-e 's/\#?(LoadModule\ dav_fs_module\ modules\/mod_dav\.so)/#\1/;' \
-e 's/\#?(LoadModule\ status_module\ modules\/mod_status\.so)/#\1/;' \
-e 's/\#?(LoadModule\ info_module\ modules\/mod_info\.so)/#\1/;' \
-e 's/\#?(LoadModule\ dav_fs_module\ modules\/mod_dav_fs\.so)/#\1/;' \
-e 's/\#?(LoadModule\ speling_module\ modules\/mod_speling\.so)/#\1/;' \
-e 's/\#?(LoadModule\ cache_module\ modules\/mod_cache.so)/#\1/;' \
-e 's/\#?(LoadModule\ disk_cache_module\ modules\/mod_disk_cache\.so)/#\1/;' \
-e 's/\#?(LoadModule\ file_cache_module\ modules\/mod_file_cache\.so)/#\1/;' \
-e 's/\#?(LoadModule\ mem_cache_module\ modules\/mod_mem_cache\.so)/#\1/;' \
-e 's/\#?(LoadModule\ version_module\ modules\/mod_version\.so)/#\1/;' /etc/httpd/conf/httpd.conf

Any time you make changes to Apache configurations, you need to restart the server in order for them to take effect:

/etc/init.d/httpd restart

Always keep in mind that automated changes and scripted suggestions can only go so far. Some level of familiarity with Apache documentation can go a long way when troubleshooting web server performance.