Why is ruby so much slower on windows?

Question

What are the specific technical causes of Ruby being so much slower on Windows? People report about a 3X speed drop from Linux/OSX and there are some vague discussions about Ruby using a compiler for Windows versions that produces slow code but I can't find any specific details.

Anybody know the specifics? I'm not interested in hurf durf Windoze sucks yuk yuks.

Answer 1

I would guess there are a few possible options, and they probably all add up:

1. Ruby being mainly developed on Linux, it ends up mechanically optimised for it. The code is regularly tested for Windows and everything works, but the result is still that developer will spend more time optimising for Linux than Windows.
2. To my experience, recent versions of gcc (4.3 and greater) produce code more efficient than recent versions of Visual Studio (at least 2005). My tests included in both case spending about a day finding the best options for code optimisation.
3. Related to point 1, if you compile the same project using gcc for Windows or Linux, I usually observe a drop of performances of about 20% on Windows compared to Linux. Here again, I suppose this is because Linux (or Unices in general) is a primary target for gcc, windows is a port. Less time is spent optimising for Windows than Linux.

In the end, if one would want to optimise Ruby for Windows, a significant amount of time (and money, as far as I know, profilers on Windows don't come for free) will have to be spent using a profiler and optimising bottlenecks. And everything will have to be tested on Linux to make sure there is no loss of performance.

Of course, all than should be tested again with their new interpreter YARV.