Earlier quoted context omitted.
I should note that the Rust version currently omits some features of the C++ version, such as read-limiting and the actual counting of the throughput. These things are cheap, but they may explain why Rust is faster in that one case.
We did some benchmarking on IRC today in light of this post and we found that Rust's stdio is currently quite slow due to a flag not being set properly in libuv which causes it to punt to a thread pool. There is currently a fix in the queue: https://github.com/mozilla/rust/pull/10558
Re: Capnproto-rust vs. C++
#11In case you get some time would appreciate a blog post or a comment describing what the issue was on the rust side as well as on the libuv side. Upvoted in advance.