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perf(lsp): Cache semantic tokens for open documents #23799

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merged 6 commits into from
May 15, 2024

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nathanwhit
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VScode will typically send a textDocument/semanticTokens/full request followed by textDocument/semanticTokens/range, and occassionally request semantic tokens even when we know nothing has changed. Semantic tokens also get refreshed on each change. Computing semantic tokens is relatively heavy in TSC, so we should avoid it as much as possible.

Caches the semantic tokens for open documents, to avoid making TSC do unnecessary work. Results in a noticeable improvement in local benchmarking

before:

Starting Deno benchmark
-> Start benchmarking lsp
   - Simple Startup/Shutdown 
      (10 runs, mean: 383ms)
   - Big Document/Several Edits 
      (5 runs, mean: 1079ms)
   - Find/Replace
      (10 runs, mean: 59ms)
   - Code Lens
      (10 runs, mean: 440ms)
   - deco-cx/apps Multiple Edits + Navigation
      (5 runs, mean: 9921ms)
<- End benchmarking lsp

after:

Starting Deno benchmark
-> Start benchmarking lsp
   - Simple Startup/Shutdown 
      (10 runs, mean: 395ms)
   - Big Document/Several Edits 
      (5 runs, mean: 1024ms)
   - Find/Replace
      (10 runs, mean: 56ms)
   - Code Lens
      (10 runs, mean: 438ms)
   - deco-cx/apps Multiple Edits + Navigation
      (5 runs, mean: 8927ms)
<- End benchmarking lsp

@nathanwhit nathanwhit added the ci-bench put this on a PR to run the benchmarks label May 14, 2024
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@dsherret dsherret left a comment

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Almost there. I think there's a slight bug in tokens_within_range

@@ -252,6 +262,7 @@ fn get_maybe_test_module_fut(
pub struct DocumentOpenData {
lsp_version: i32,
maybe_parsed_source: Option<ParsedSourceResult>,
maybe_semantic_tokens: Arc<Mutex<Option<lsp::SemanticTokens>>>,
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Might be nice to add something like CloneCell<T: Send + Clone> to cli::util::sync that has methods like set(value: T) and get_cloned(&self): T in order to bury the mutex there.

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That said, should this use something like OnceCell instead? I guess no because async.

cli/lsp/semantic_tokens.rs Show resolved Hide resolved
cli/lsp/semantic_tokens.rs Show resolved Hide resolved
}),
);

assert_eq!(res, res_cached);
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How are we integration testing whether or not a cache is being used? Shouldn't the result be the same?

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Added some code to the test client to collect performance markers, so we can assert on how many times tsc.request.getEncodedSemanticClassifications has been called

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LGTM

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@nayeemrmn nayeemrmn left a comment

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LGTM

@nathanwhit nathanwhit enabled auto-merge (squash) May 15, 2024 01:24
@nathanwhit nathanwhit merged commit 36d877b into denoland:main May 15, 2024
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bartlomieju pushed a commit that referenced this pull request May 16, 2024
VScode will typically send a `textDocument/semanticTokens/full` request
followed by `textDocument/semanticTokens/range`, and occassionally
request semantic tokens even when we know nothing has changed. Semantic
tokens also get refreshed on each change. Computing semantic tokens is
relatively heavy in TSC, so we should avoid it as much as possible.

Caches the semantic tokens for open documents, to avoid making TSC do
unnecessary work. Results in a noticeable improvement in local
benchmarking

before:
```
Starting Deno benchmark
-> Start benchmarking lsp
   - Simple Startup/Shutdown 
      (10 runs, mean: 383ms)
   - Big Document/Several Edits 
      (5 runs, mean: 1079ms)
   - Find/Replace
      (10 runs, mean: 59ms)
   - Code Lens
      (10 runs, mean: 440ms)
   - deco-cx/apps Multiple Edits + Navigation
      (5 runs, mean: 9921ms)
<- End benchmarking lsp
```

after:
```
Starting Deno benchmark
-> Start benchmarking lsp
   - Simple Startup/Shutdown 
      (10 runs, mean: 395ms)
   - Big Document/Several Edits 
      (5 runs, mean: 1024ms)
   - Find/Replace
      (10 runs, mean: 56ms)
   - Code Lens
      (10 runs, mean: 438ms)
   - deco-cx/apps Multiple Edits + Navigation
      (5 runs, mean: 8927ms)
<- End benchmarking lsp
```
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3 participants