What do you mean by "prefetched SVN versioning info"?
I have a fairly large rails project, but I've been struggling with memory usage in the last while - each process shows nearly 200 megs of VSIZ, and 110 megs of RSS. They start around 94/44, but grow from there. Some requests load a thousand small objects, but it shouldn't be growing that much. I just wondered if your mention might be the clue to my problems too!