Though big enough to be worthwhile at scale, it's notable how small, relatively, the difference is from the out-of-box Rust unstable sort to the tuned radix sort.
Lukas Bergdoll and Orson Peters did some really important heavy lifting to get this stuff from "If you're an expert you could probably tune a general purpose sort to have these nice properties" to "Rust's general purpose sort has these properties out of the box" and that's going to make a real difference to a lot of software that would never get hand tuned.
Well, years back I released an unstable sort called pdqsort in C++. Then stjepang ported it to the Rust standard library. So at first... nothing. Someone else did it.
A couple years later I was doing my PhD and I spent a lot of time optimizing a stable sort called glidesort. Around the same time Lukas Bergdoll started work on their own and started providing candidate PRs to improve the standard library sort. I reached out to him and we agreed to collaborate instead of compete, and it ended up working out nicely I'd say.
Ultimately I like tinkering with things and making them fast. I actually really like reinventing the wheel, find out why it has the shape that it does, and see if there's anything left to improve.
But it feels a bit sad to do all that work only for it to disappear into the void. It makes me the happiest if people actually use the things I build, and there's no broader path to getting things in people's hands than if it powers the standard library.
Lukas Bergdoll and Orson Peters did some really important heavy lifting to get this stuff from "If you're an expert you could probably tune a general purpose sort to have these nice properties" to "Rust's general purpose sort has these properties out of the box" and that's going to make a real difference to a lot of software that would never get hand tuned.