slightly related: earlier I was experimenting with Rust string allocations, even though my code did almost same as standard library, the heap allocations were taking 10x of time. Relevant code:

  fn alloc_string(s: &str) -> NonNull<u8> {
      let boxed_slice = s.as_bytes().to_owned().into_boxed_slice();
      NonNull::new(Box::into_raw(boxed_slice) as *mut u8).unwrap()
  }

Approximately, if stdlib was taking 1µs, but my code was about 14-15µs for large strings. Profiling also did not help. Anyone have any guesses? Here is the full code: https://github.com/avinassh/string-alloc