David Heinemeier Hansson wrote:

> Rails caches the compiled ERb and reuses the structure such that a new 
> run merely requires a run on the passed bindings. But there's no 
> explicit byte code caching beyond whatever Ruby itself may be doing.
>
I always assumed that would be the case. It is, however, not entirely 
true. At the moment it just caches the source code of the compiled ERb 
and does an eval on that, which means it will be reparsed on each 
request. But there is a patch available here: 
http://dev.rubyonrails.org/ticket/912

-- Stefan Kaes