Improve Page Speed With mod_pagespeed

Posted by Des Mc Carthy on 30 November 2010

About a year ago Google announced that it had started using page speed as one of over 200 signals that it considers when determining search ranking. While it is thought not to have a huge influence on search results, it was deemed important enough to include in Google's Webmaster tool set (labs Dec 2009).

From the user experience point of view, the faster the web page loads the better and this will have a knock on effect of increasing conversion rates.  These two things are pretty good reasons to look at speeding up your website. But where to begin?

Lately (Nov 2010) Google released an apache module "mod_pagespeed" to help with improving page load speeds. mod_pagespeed works by optimising the requested web page before it is sent to the clients browser and caching the results for future requests. This will obviously increase the loading on the web server and may not be suitable for all configurations. However in the tests I performed, this really wasn't an issue as there was plenty of spare capacity, also beware mod_pagespeed is still in beta.

Installation on Centos 5.5

• Login to your server using SSH and sudo root
• Check that AT is installed on your system - yum list at
• If AT is not present then install - yum install at
• Download rpm from google - wget https://dl-ssl.google.com/dl/linux/direct/mod-pagespeed-beta_current_i386.rpm
• Install rpm - rpm -i mod-pagespeed-*.rpm
• AT will schedule the install to run in one minute

The installation adds the Google repository to your yum repositories, simplifying future updates.

Configuration

The installed rpm places the mod_pagespeed.so  in /usr/lib/httpd/modules/ , I left it there as I was not sure what effect it would have moving it to /etc/httpd/modules. The apache config file mod_pagespeed.conf can be found in /etc/httpd/conf.d

In the pagespeed.conf around lines 20&21 you will find the following configs for the cache directory.

Apache needs write access to these directories

• ModPagespeedFileCachePath            "/var/www/mod_pagespeed/cache/"
• ModPagespeedGeneratedFilePrefix    "/var/www/mod_pagespeed/files/"

That should be enough to get us started. Restart your web server - service httpd restart

Testing

To see if mod_pagespeed is correctly installed and working, request a page from your website and see if there are files in the cache directory and check your phpinfo page. This should show "X-Mod-Pagespeed" in the http header response section.

Conclusion

I found that pages on my test site loaded 25%-40% faster with the above configuration.

When I added filters

• ModPagespeedEnableFilters rewrite_css,rewrite_javascript
• ModPagespeedEnableFilters collapse_whitespace

to my config file I got a further 10%. So all-in-all I achieved a 50% increase in page loading site wide for half an hour's work. NOT BAD AT ALL. I will be monitoring Google's webmaster tools and will publish the graph displaying load speeds in a few weeks.

Here is a youtube video released by google showing side-by-side comparsion of a site loading with and without mod_pagespeed