There are always exceptions, programming for the PS3 was... interesting given the SPUs didn't have any caches, although one could argue they were closer to DSPs

There are always exceptions, programming for the PS3 was... interesting given the SPUs didn't have any caches, although one could argue they were closer to DSPs with the manual DMA required. I'm not really interested in arguing semantics but more that those languages tend to be what you see modern, battle-tested OSes developed in. My point is if you're not using C/C++/Rust what are you using that exposes those concepts? Not saying you can't do those things in other languages(I've shipped cache-aware datastructures at scale in Java using ByteBuffers + flatbuffers) however you're having to reach through abstractions and/or other limitations. Say nothing that on most OSes that C tends to be the OS ABI as well.