Unicorn and thin are both written in ruby with the core being the ragel HTTP parser which was first implemented in mongrel. Thin took that ragel parser and adde

Unicorn and thin are both written in ruby with the core being the ragel HTTP parser which was first implemented in mongrel. Thin took that ragel parser and added eventmachine to the mix which made it much faster the mongrel. Unicorn went a step further by leveraging the kernel in such a way that things got even faster. Macournoyer, creator of thin was working on thin-turbo, a rewrite of the thin backend in C but stopped a while back. Passenger I guess because its nginx or apache module has to be C but their focus was never performance, more ease of deployment. Passenger 3 will have performance improvements and they've got benchmarks here http://blog.phusion.nl/2010/06/10/the-road-to-passenger-3-technology-preview-1-performance-2/ http://blog.phusion.nl/2010/06/10/the-road-to-passenger-3-te... but I'm thinking mongrel2 will one up it.