[ruby-core:35961] require performance on 1.9

Hello,
I am looking into the performance issues requiring files in 1.9.
Here is a graph I am trying to fix:
https://skitch.com/xaviershay/rh64d/tc-load-time
https://gist.github.com/c8d0d422a9203e1fe492 (after creating 10000 files 
in the `f` dir)

A commit from a few years back [1] adds some behaviour around 
loaded_feature_path. When disabled, the require time in my benchmark is 
halved [2]. There is no test covering this behaviour, and I can't quite 
figure out what it is doing.

It is probably explained in ruby-dev:31932 but I can't read Japanese:
http://markmail.org/message/d3ef53c63kx2xqkr

Can anyone either translate the above message for me, or provide a test 
case that covers the expected behaviour?

Cheers,
Xavier

P.S. This may or many not be related to this issue:
http://redmine.ruby-lang.org/issues/show/3924

[1] 
https://github.com/ruby/ruby/commit/bb1f1c57823758d2450d184ce7c85beb0d538bf0

[2]  add continue; to load.c:161 gives 3s for n=2500