You can use arena allocators in Rust: bumpalo is popular. And it's easy to send objects off to a separate thread to be destroyed if that's what you desire: just send them over a channel to another thread (though this is really something that the malloc implementation should do internally if it's a win). There's an RFC for multiple allocators that has had some implementation work done lately: https://rust-lang.github.io/rfcs/1398-kinds-of-allocators.ht...

I don't believe that that 8kB number is with UPX, but again, even if Rust produces smaller binaries than C, it doesn't matter. Most users would prefer faster compilation times with codegen-units over a few kB smaller binaries, for instance, as long as there's a reasonable way to get the smaller binaries for those who need them.