Apache Module mod_deflate

Looking to tune the apache for performance, then this should help you out.

The mod_deflate module provides the DEFLATE output filter that allows output from your server to be compressed before being sent to the client over the network


This is a simple sample configuration for the impatient.
Compress only a few types

AddOutputFilterByType DEFLATE text/html text/plain text/xml

The following configuration, while resulting in more compressed content, is also much more complicated. Do not use this unless you fully understand all the configuration details.
Compress everything except images


# Insert filter
SetOutputFilter DEFLATE

# Netscape 4.x has some problems...
BrowserMatch ^Mozilla/4 gzip-only-text/html

# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0[678] no-gzip

# MSIE masquerades as Netscape, but it is fine
# BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

# NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48
# the above regex won't work. You can use the following
# workaround to get the desired effect:
BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html

# Don't compress images
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png)$ no-gzip dont-vary

# Make sure proxies don't deliver the wrong content
Header append Vary User-Agent env=!dont-vary

Apache <IfDefine> Directive

This is used to process some section in httpd.conf based on the system argument.

The directives within an <ifdefine></ifdefine> section are only processed if the "test" variable is true. If "test" variable is false, everything between the start and end markers is ignored.

Example:

httpd -D test -k start

Starting the httpd with system parameter "test" will execute the below section or else it will skip those
<ifdefined>
...
...
</ifdefined>

This will be useful sometime when you try loading modules on specific arguments.