Discussed at the time:
The benefits and costs of writing a POSIX kernel in a high-level language - https://news.ycombinator.com/item?id=18171447 - Oct 2018 (96 comments)
The benefits and costs of writing a POSIX kernel in a high-level language - https://news.ycombinator.com/item?id=18171447 - Oct 2018 (96 comments)
Top comment from the linked thread.
This is a bit out of context. 5-15% in any measurements to mainstream software is too easy. Even if it's operating system. We all know that.
This is why almost any papers that compare a research project's products with a mainstream production one in terms of performance is usually just for establishing context than actually comparison.