From: Chris White <cwprogram@...>
Date: 2011-08-08T00:01:51+09:00
Subject: Re: Methods defined with module_eval are... faster?

Yes that's correct. In order to understand the logic it's important to take a look at the resulting bytecode, as benchmarks can get a little weird. First the non-module_eval version:

https://gist.github.com/fc559c8a92336e382777

Resulting bytecode:

https://gist.github.com/1130430

As shown here, the method is created, then attached to the module. Now the module_eval version:

https://gist.github.com/1130424

Resulting bytecode:

https://gist.github.com/1130432

Now here, instead of creating a method and attaching it the module, it's instead just putting a string with the code on the stack and sending it off to module_eval. This hits the C side of ruby in the following manner:

https://gist.github.com/1130437

So in essence it means more time is spent in the C side instead of a back and forth chain of bytecode calls. Note that all bytecode is produced via MRI 1.9.3. Honestly though the difference between the two using the benchmark was minimal enough that I don't think it's anything to be worried over. Also note that syntax highlighters will see the eval string as what it is, a literal string. This will make your code less readable!

Regards,
Chris White
Twitter: http://www.twitter.com/cwgem