[beng-nl]

This is a tangent, because it clearly didn’t pan out, but I had hope for rust having an edge when I learned about how all objects are known to be immutable or not. This means all the mutable objects can be held together, as well as the immutable, and we’d have more efficient use of the cache: memory writes to mutable objects share the cache with other mutable objects, not immutable Objects, and the bandwidth isn’t wasted on writing back bytes of immutable objects that will never change.

As I don’t see any reason rust would be limited in runtime execution compared to c, I was hoping for this proving an edge.

Apparently not a big of an effect as I hoped.

[rcxdude]

I think it would be quite difficult to actually arrange the memory layout to take advantage of this in a useful way. Mutable/immutable is very context-dependent in rust.

[pornel]

Rust doesn't have immutable memory, only access restrictions. An exclusive owner of an object can always mutate it, or can lend temporary read-only access to it. So the same memory may flip between exclusive-write and shared-read back and forth.

It's an interesting optimization, but not something that could be done directly.