Some tips to find memory leaks in Rails:
- use the Bleak House plugin
- implement Scout monitoring specifically the memory usage profiler
- try another simple memory usage logger
The first is a graphical exploration of memory usage by objects in the ObjectSpace.
The last two will help you identify specific usage patterns that are inflating memory usage, and you can work from there.
As for specific coding-patterns, from experience you have to watch anything that’s dealing with file io, image processing, working with massive strings and the like.
I would check whether you are using the most appropriate XML library – ReXML is known to be slow and believed to be leaky (I have no proof of that!). Also check whether you can memoize expensive operations.