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https://blog.heroku.com/ruby-3-by-3/ https://blog.heroku.com/ruby-3-by-3/
https://blog.heroku.com/ruby-3-by-3/ https://blog.heroku.com/ruby-3-by-3/
Fair warning: this is from 4 years ago.
That's rather vague. But yes, no matter which JIT you always need some extra memory to run the JIT, and it creates a more optimized version while also needing the unoptimized version of the code, so it needs more memory.