Great work to the ruby team, the improvements in Ruby's performance since 2.x have been very impressive to say the least. Well done and Merry Christmas to everyone that worked hard on this release.
I just popped off a branch of my production Rails 4.1.8 app (Can't quite do 4.2 yet), and upgraded it 2 Ruby 2.2. I ran 271 spec against it 5 times before the upgrade and 16 times after. I should have done more before :(
For 2.1.5
AVG: 18.02
MEDIAN: 18.11
MIN: 16.26
MAX: 19.6
For 2.2
AVG: 18.162~
MEDIAN: 15.23
MIN: 14.44 <- nice
MAX: 47.03 <- first run, wut?
It looks better, but I haven't profiled the app on Passenger yet to see how well it plays with the whole app.