My experience is that if you don't need JRuby (for Java interop or to satisfy pointy-haired strictures), you probably won't see much benefit from choosing it, at least for a Rails app.
On one hand, JRuby is technically a much better Ruby than Ruby, and if you want to improve bulk throughput you'll probably benefit. On the other, if bulk throughput were important, Ruby probably wouldn't be your first choice, and there are some downsides.
The biggest problem, especially for Rails, is the warm-up cost. Rails's start-up time is already painful, and adding to that hardly improves the test-develop cycle. I've not tested this latest release, but in 1.6.8, running a test suite was multiples slower than C Ruby. Test suites, which run a lot of different code, aren't really representative of real-world workloads, but if you're working on an application it really hurts.
You might also have trouble with gems that have compiled extensions. It takes a bit of Gemfile fiddling, but there are alternatives to most of those.
For applications other than Rails (which is really a bit of a pathological case), JRuby seems well worth a look. I've never found C Ruby's threading up to the job of making a responsive GUI application, but JRuby might work a lot better with its JVM-backed threads.
Comments
My experience is that if you don't need JRuby (for Java interop or to satisfy pointy-haired strictures), you probably won't see much benefit from choosing it, at least for a Rails app.
On one hand, JRuby is technically a much better Ruby than Ruby, and if you want to improve bulk throughput you'll probably benefit. On the other, if bulk throughput were important, Ruby probably wouldn't be your first choice, and there are some downsides.
The biggest problem, especially for Rails, is the warm-up cost. Rails's start-up time is already painful, and adding to that hardly improves the test-develop cycle. I've not tested this latest release, but in 1.6.8, running a test suite was multiples slower than C Ruby. Test suites, which run a lot of different code, aren't really representative of real-world workloads, but if you're working on an application it really hurts.
You might also have trouble with gems that have compiled extensions. It takes a bit of Gemfile fiddling, but there are alternatives to most of those.
For applications other than Rails (which is really a bit of a pathological case), JRuby seems well worth a look. I've never found C Ruby's threading up to the job of making a responsive GUI application, but JRuby might work a lot better with its JVM-backed threads.