Improve style resolution performance #453
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This uses a simple cache to keep track of already-computed scope stacks, which greatly improves the efficiency of computing of new styles (at some cost in memory.)
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This looks reasonable to me. One caveat: I don't remember why we went with this approach instead of using the pushes/pops I use in syntect. I know we discussed it a bunch, but I can't comment knowing that.
Also I seem to recall that at some point in that discussion I did benchmarks on how many different stacks you could expect to see in typical and atypical files. If you find the right old issue discussion you may find a comment with those results. That may inform concerns about memory.
| // a prefix tree. | ||
| /// style state of existing scope spans, so we can more efficiently | ||
| /// compute styles of child spans. | ||
| style_cache: HashMap<Vec<Scope>, StyleModifier>, |
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If hashing shows up any significant amount in the time profile, you can switch this to use a FNV hasher, which is what I use in syntect.
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@trishume okay, good note, thanks!
This patch significantly improves the speed at which we resolve scope spans into styles and greatly improves startup performance, especially noticeable on debug builds.
before:
after: