I suspect the issue is Iron, though rust-http certainly isn't helping much. Here are some graphs, generated from data made by rust-http's benchmarking script (https://github.com/chris-morgan/rust-http/tree/master/compar...), on my box.

A spreadsheet: https://docs.google.com/spreadsheets/d/1-5_4wPPKNBYZ6yuw-rRl... The raw data: https://gist.github.com/cmr/3648bcc6365c1dba83f1

The charts themselves: http://imgur.com/gw1mp40,Hn3929i,h2OQiTh

Software versions:

rustc 0.11.0-pre (44ec28cfac9fa3f738e0e77ccca1d804125fd1dd 2014-07-01 21:26:33 +0000)

go version go1.3 linux/amd64

node v0.10.29

Apache 2.4.9

wrk 3.1.0

Arch Linux, x86_64, CPU: https://gist.github.com/cmr/7cc6df806caff2253667