Er… yes? Did I say it was unimportant anywhere? (also please note that I'm not a Rust developer)
> Does Rust allow using memory allocated by specific external allocators? i.e. libnuma or something?
I'm not quite sure what you're asking
* if you're asking if it's possible to use arbitrary memory returned by a third party? Then yes.
* if you're asking whether user-defined allocators or boxes are supported and you can ask the runtime to put its stuff in memory you get from e.g. a bundled jemalloc, then that's planned but not in I believe: https://github.com/mozilla/rust/issues/12038
No, but that link seemed to indicate it wasn't being planned for the first release and pcwalton seems to think it's possible to get Rust programs to run as fast as C++ programs in most cases.
(The speed of a language isn't determined by the speed of it's "first release".)
There is certainly a set of performance-critical problems where making optimal use of vector instructions is essential. It does seem that Rust is unlikely to be competitive for those today. But i think it's a minority of all problems.
Does Rust allow using memory allocated by specific external allocators? i.e. libnuma or something?