One of the biggest problems with the 1.8.x versions of MRI (or CRuby as it's referred to in this article) is that the GC is pretty slow and tends to get called

One of the biggest problems with the 1.8.x versions of MRI (or CRuby as it's referred to in this article) is that the GC is pretty slow and tends to get called a lot. A good explanation of the reasons behind that can be found here: http://www.engineyard.com/blog/2010/mri-memory-allocation-a-primer-for-developers/ http://www.engineyard.com/blog/2010/mri-memory-allocation-a-... As Rails got more popular and sites built on Rails got bigger, people started running into performance issues that could often be rooted down to GC being called over and over during a single web request (due to instantiation of lots of AR objects, causing lots of memory allocations which lead to GC being called.) This lead to people exploring other implementations of Ruby (REE, Rubinius, etc.) and more importantly, becoming a lot more familiar with how GC works in MRI and how to program around it's shortcomings.