In running a cpu heavy math benchmark against 1.7.20.1 and 9.0.0.0.rc1 I've observed a significant performance regression. The 9.0.0.0.rc1 times are 1.5 to 2.5 slower than for 1.7.20.1.

Here is a gist of the benchmark, justdo load 'primalitytest.rb' and it will run.
https://gist.github.com/jzakiya/9befd7eb5ed9640f9358

This code became the precursor to a gem I released on April 1, 2015 -- primes-utils.
I see the same performance degradation with its methods as with the above benchmark methods.

I know 9.0.0.0 is still a first release candidate but this seems very extreme to me.

jz