Our understanding is that when running Passenger, simply passing '-e production' to the command line is sufficient to run in production, but if that's incorrect, we'll gladly update the test.
Something else you might consider is the OJ gem rather than just the stock Ruby json gem. The latter is notoriously slow and memory-hungry (which will compound the GC issues!)
Could you elaborate on this, or point me in the right direction? I'm learning Rails and curious.
Ruby allocates heaps for its objects, and sets GC thresholds based on those heap sizes. Ruby allows you to change those settings via environment variables, which means that you can end up doing fewer allocations and less aggressive GC, which makes sense when using a full framework like Rails, which is going to allocate a lot of objects.
There's a more complete answer here to get you started: http://stackoverflow.com/questions/13387664/ruby-gc-executio...