I’ve put together a somewhat extensive collection of scripts and results from looking at how often objects get garbage collected in Ruby 1.8 and Ruby 1.9. Performance metrics are also provided running the script under various different environments, which I found quite fascinating. irb, for instance, is ridiculously slow. Granted, the vast majority of these scripts times are spent performing very inefficient ObjectSpace calls, so the raw numbers should be taken with a grain of salt. The metrics are only interesting for comparison, and are of questionable use.

This was instigated by a String versus Symbol discussion in #ruby on Freenode. The individual was primarily worried about memory usage, and these scripts confirm that strings will get garbage collected often and quickly.

One thing to note is how Ruby 1.8 changes its thresholds for garbage collection under each environment, which may be based on the amount of objects in global space that it cannot garbage collect. Under Ruby 1.9, the results are bit more consistent, although this may be due to better metrics being available in Ruby 1.9.