Simple web server benchmark - vibe.d is slower than node.js and Go?

[Vadim Lopatin]

There is a simple set of simple web server apps written in 
several languages (Go, Rust, Scala, Node-js):

https://github.com/nuald/simple-web-benchmark

I've sent PR to include D benchmark (vibe.d).

I was hoping it could show performance at least not worse than 
other languages.
But it appears to be slower than Go and even Node.js

Are there any tips to achieve better performance in this test?

Under windows, I can get vibe.d configured to use libevent to 
show results comparable with Go. With other configurations, it 
works two times slower.

Under linux, vibe.d shows 45K requests/seconds, and Go - 50K. The 
only advantage of D here is CPU load - 90% vs 120% in Go.

I'm using DMD. Probably, ldc could speed up it a bit.

Probably, it's caused by single threaded async implementation 
while other languages are using parallel handling of requests?