On his blog post he looks at both the micro benchmarks and overall benchmarks. The summarized results:
IronRuby went from being much slower than Ruby MRI to considerably faster across nearly all the tests. That’s major progress for sure, and the team behind the project deserves mad props for it.
One final warning before we get too excited here. IronRuby is not faster than Ruby 1.9.1 at this stage. Don’t let that first chart mislead you. While it’s faster in certain tests, it’s also slower is many others. Currently, it’s situated between Ruby 1.8.6 and Ruby 1.9.1, but much closer to the latter. The reason why this chart is misleading is that it doesn’t take into account any tests that timed out, and several of such timeouts were caused by IronRuby (more than those caused by Ruby 1.9.1). If you were to add, say, 300 seconds to the total, for each timeout for the two implementations, you’d quickly see that Ruby 1.9.1 still has the edge. The second chart that compares macro-benchmarks does a better job at realistically showing how IronRuby sits between Ruby 1.8.6 and Ruby 1.9.1 from a performance standpoint. If you were to plot every single benchmark on a chart, you’d find a similar outcomes for a large percentage of the tests.
Whether it’s faster than Ruby 1.9 or not, now that good performances are staring to show up, it’s easier to see IronRuby delivering on it’s goal of becoming the main implementation choice for those who both develop and deploy on Windows. This, paired with the .NET and possible Visual Studio integration, the great tools available to .NET developers, and the ability to execute Ruby code in the browser client-side thanks to projects like Silverlight/Moonlight and Gestalt, make the project all the more interesting.