Box to save memory in Rust
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Box to save memory in Rust
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Re: Box to save memory in Rust
#2[Edit:deleted]
Re: Box to save memory in Rust
#3[Edit:deleted]
Box is still two words (length and pointer). That's better than the 3 words (length, pointer, capacity) for strings, but Box is one word (not including the heap allocation).
Re: Box to save memory in Rust
#4Are 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"
Re: Box to save memory in Rust
#5Are 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.
Re: Box to save memory in Rust
#6Are 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…
Specifically this lint: https://rust-lang.github.io/rust-clippy/master/index.html#la...
Re: Box to save memory in Rust
#7Re: Box to save memory in Rust
#8I wonder from time to time whether you can decide the best “schema shape” beforehand, ie before you can run real workloads that stress the memory implications of such things. This can be very useful if you are trying to decide the boundary of some public facing API, but for whatever reason can’t run benchmarks (lack of impl, data, time, etc).
Without that, if you try to suggest a transformation like this when the schema is first conceived, it will likely be considered premature optimization.
Re: Box to save memory in Rust
#9tbh "trait" feels like a very problematic name for that type, for this kind of educational purpose - `trait` is already an established concept and keyword: https://doc.rust-lang.org/book/ch10-02-traits.html
It's especially problematic because traits don't have memory behaviors like this article in most cases - by default they're unsized, because it's a description of behavior, not data, and you can't even use them as a struct field without extra work.
Like, replace "trait" in here with "box" and see how confusing it would be to be describing how you saved memory by boxing your box, because option doesn't box like many other languages do.
Re: Box to save memory in Rust
#10I quite often have this issue with async. You get a state machine that is huge because of how Rust builds it.