Are there any tools that help finding these kinds of things? Like a profiler that says "80% of the allocated bytes are objects of this type, with 95% of those having that field set to None"
The closest I am aware of is clippy (`cargo clippy` in a standard Rust project will run it with default configurations).
Clippy is essentially a linter; and one of its checks catches cases where different enum variants have a significantly different size; with a suggestion to Box the larger variant.
Since this is just a linter, it doesn't actually have any knowledge of how frequently each variant is actually used. It also doesn't address the situation in the article at all.
Box<str> is still two words (length and pointer). That's better than the 3 words (length, pointer, capacity) for strings, but Box<String> is one word (not including the heap allocation).
Are there any tools that help finding these kinds of things? Like a profiler that says "80% of the allocated bytes are objects of this type, with 95% of those having that field set to None"
The closest I am aware of is clippy (`cargo clippy` in a standard Rust project will run it with default configurations).
Clippy is essentially a linter; and one of its checks catches cases where different enum variants have a significantly different size; with a suggestion to Box the larger variant.
Since this is just a linter, it doesn't actually have any knowledge of how frequently each variant is actually used. It also doesn't address the situation in the article at all.
Specifically this lint: https://rust-lang.github.io/rust-clippy/master/index.html#la...
Box<str> or Box<&str> might also have been usable routes. (example: https://play.rust-lang.org/?version=stable&mode=debug&editio... )
Box<str> is still two words (length and pointer). That's better than the 3 words (length, pointer, capacity) for strings, but Box<String> is one word (not including the heap allocation).