These are the slides from a talk done at the Free Software and Open Source Symposium (FSOSS) at Seneca College in Toronto. The attendance was overwhelming with several people standing at the back of the room.

The talk is titled: Open Source for Fun and Profit: making a career out of FOSS, and draws heavily from Khalid's experiences in the Drupal community.

We have posted before on how to display previous/next thumbnails for image nodes. We also have a module that is basically a Previous/Next API for high volume / high performance sites.

But sometimes you need a simpler solution for regular nodes, just using the node title and a link to it. This article explains how to achieve that for Drupal 6 in one simple function and a few changes to one .tpl.php file.

First, we start off with the code that does the heavy lifting.

In your theme's template.php add the first function from the attached file. By default it provides paging for blog posts only. You can change that to another type of node (or multiple types).

The code is fast, since it uses the nid as an index. So if you use this on large sites, it would not slow them down.

Then in your node.tpl.php, or node-TYPE.tpl.php, add the second snippet in the attached file. This provides calls to the next/previous node with hyperlinked titles.

For the styling, add the CSS from last snippet in the attached file.

A very large site we manage for a client was upgraded recently from the memcache module version 1.12 to version 1.13.

However, the result was less performance for this server that was humming alone happily with the older version.

The Munin graphs tell it all: look at the change at 12:00 noon.

Here is the CPU graph, showing double the CPU utilization on this sever.

Performance troubleshooting and tuning of web sites is often, to paraphrase Winston Churchill, "a puzzle inside a riddle, wrapped in an enigma".

One of those puzzles is how sites are put together: in this case: multiple layers of modules that obscure the real cause of where the slowness of a site is, and a theme for the topping.

Problem and symptoms