LSP perf optimizations by andrewbranch · Pull Request #64877 · microsoft/TypeScript

Andrew Branch (andrewbranch) · 2026-10-19T19:12:56Z

I let Copilot spin for a while on LSP performance, profiling the vscode repo. Several of these changes affect batch compilation too.

Baseline (vscode)

Bench	time/op	B/op	allocs/op
InitialLoad	1.2–2.5 s	3.04 GB (2595 MB retained)	–
EditOpenFile	13–22 ms	14 MB	–
EditImports	115–146 ms	277 MB	3.26 M
WatchChange	6–8 ms	–	–
CreateDeleteFile	335–375 ms	291 MB	3.46 M
TsconfigChange	~339 ms	–	–

Heap of initial load: ~95% of retained memory is ASTs/symbols in the parse cache (core compiler).
Project-package retained structures are small; the project package's leverage is mostly transient
allocation and per-change latency.

Cumulative result (merge-base `3789ddb` vs HEAD, vscode, interleaved runs, n=6)

Bench	time	B/op	allocs/op	retained
InitialLoad	~ (1.29 → 1.15 s, noisy)	−3.7%	−15.6%	−2 MB (of 2.4 GB)
EditOpenFile (fast clone)	~	−4.9%	−23.3%	−24% (14.0 → 10.7 MB)
WatchChange (fast clone from disk)	~ (3–4 ms, noisy)	−16.0%	−90.4%	–
EditImports (program rebuild)	~/−19%*	−37.6%	−41.8%	−17%
CreateDeleteFile (file-name reload + rebuild)	−43%	−38.6%	−41.2%	−12%
TsconfigChange (ParsedCommandLine + rebuild)	−40%	−38.9%	−41.4%	−12%
AutoImportInitial	~	−3.1%	−0.5%	−15.6% (19.8 → 16.7 MB)
AutoImportEdit	~	−4.8%	−44.1%	–

* EditImports: 165 → 97 ms in a direct A/B of the final fix; ~ in the noisy cumulative run.
Timings were taken with load average 10–20 from other processes; B/op and allocs/op are exact.

Experiments

1. `dirty.SyncMap.LoadClean` fast path in snapshotFSBuilder — COMMITTED (`0a35842`; benchmarks in dd354e654af)

dirty.SyncMap.Load allocates a SyncMapEntry wrapper on every hit in the immutable base map.
snapshotFSBuilder's GetFileByPath/FileExists/GetAccessibleEntries only need read access, so
added LoadClean returning the base value without allocation when the key is not dirty.

EditImports allocs −4.7%; CreateDeleteFile allocs −4.6%, time −4.6%; B/op −1.9%.

2. parseTask hot/cold split (compiler/filesparser.go) — COMMITTED (`cea07f4`)

Program rebuild profile showed parseTask allocations prominent. Removed two dead fields and moved
load-result fields to a lazily allocated *parseTaskResult (only tasks that actually load need
them; failed-lookup/duplicate tasks don't). parseTask 368 B → 184 B.

EditImports / CreateDeleteFile B/op −7.4%, allocs +0.3%. Timing within noise.

3. Concurrent directory prefetch in vfsmatch — COMMITTED (`39911ff`)

CPU profile of CreateDeleteFile/TsconfigChange: ~80% of updateProgram CPU is
ReloadFileNamesOfParsedCommandLine → vfsmatch.matchFileNames → sequential os.ReadDir
over the whole include tree (snapshot cachedvfs is fresh per snapshot, so it hits disk every time).
Added a prefetch phase that reads the same directories concurrently, then the original
serial walk runs unchanged using the prefetched entries (falling back to the host for anything
missing). Results/ordering/symlink-cycle semantics are unchanged.

CreateDeleteFile 374 → 218 ms, TsconfigChange 354 → 178 ms (p=0.002, wide variance).
B/op +1%, allocs +0.5% (prefetch bookkeeping).
Also benefits initial load and tsc CLI config parsing.

4. sourceFS seen-file tracking + overlayFS no-clone — COMMITTED (`039e5dd`)

sourceFS.FileExists computed a PathKey for tracking and again for the lookup, and stored into
seenFiles unconditionally. Compute the key once, Load before Store; overlayFS stopped cloning
its overlay map on read paths.

Rebuild benches allocs −2–3%, B/op −2%.

5. packagejson.InfoCache cheap Clone — COMMITTED (`14e9882`; RWMutex variant squashed away)

ReuseProgram (every edit / watch change) clones the package.json info cache; cloning a
sync.Map entry-by-entry allocated per entry (~6.6k allocs per WatchChange).

First version (RWMutex + plain map): WatchChange −30% time, −90% allocs; EditOpenFile −14% time.
But EditImports regressed +38% time (119 → 165 ms): RWMutex reader-count contention during
parallel module resolution. Found only via a cumulative merge-base A/B + bisect — lesson: every
concurrency-touching change needs a rebuild-heavy timing check.
Final version: immutable base map read lock-free + collections.SyncMap overlay for new entries;
Clone = maps.Clone(base) + overlay merge. Keeps clone wins; EditImports 165 → 97 ms
(faster than the original 119 ms), −2% allocs. -race clean.

6. autoimport `Export` 248 → 192 B — COMMITTED (`b975755`)

Registry retained memory is dominated by Export (~52k exports on vscode). ModuleID stores one
string + kind instead of two strings; ExportSyntax, lsutil.ScriptElementKind narrowed to uint8;
fields reordered to remove padding.

AutoImportInitial retained −15.7% (19.8 → 16.7 MB). Time/allocs unchanged.

7. tsoptions extension-priority sibling keys — COMMITTED (`c09c9b0`)

getFileNamesFromConfigSpecs built ChangeExtension + canonical key for each higher/lower-priority
sibling of every wildcard file and appended a flattened group slice per file (~57% of file-name
expansion allocs). Now derives sibling keys from one canonical key (stemKey + ext, falling back to
the old path for unknown extensions / dynamic names), iterating groups in place.
Verified with a temporary 20k-case randomized differential test against the old implementation.

TsconfigChange / CreateDeleteFile B/op −2.1%, allocs −1.8%.

8. Module resolution: resolve candidate once — COMMITTED (`de88374`)

resolutionCandidateFromEncodedPaths resolved the same relative specifier twice (ResolveFile and
ResolveDirectory) whenever the file and directory inputs were identical (always, outside dynamic
files); both produce identical strings. Resolve once.

TsconfigChange B/op −12.8%, allocs −13.2%, time −10%; InitialLoad allocs −5%, time −11%.

9. tspath leading `./` / `../` fast path — COMMITTED (`9496c1e`)

ResolveFile/ResolveDirectory for ./x, ../../x concatenated then normalized (2 allocs). Now
walks the directory up for leading dot segments and concatenates once; falls back for any other dot
segments or ascending past root. 200k-case randomized differential test (disk, drive, URL, UNC,
dynamic roots) against the old path.

TsconfigChange B/op −12.1%, allocs −12.9%, time −8%; InitialLoad allocs −4.8%, time −9%.

10. parseTask references resolution PackageId — COMMITTED (`02e334f`)

parseTask/resolvedRef carried a 64 B inline PackageId (empty for nearly all files). Now a
pointer into the already-heap-allocated resolution (nil when empty). parseTask 184 → 136 B
(192 → 144 size class), no new allocations.

TsconfigChange B/op −3.8%.

11. Co-allocated referenced-file include reasons — COMMITTED (`570e356`)

Each import allocated FileIncludeReason (56 B) + referencedFileData (32 B) separately; both are
retained by the program. fileIncludeKind → uint8 (48 B) and one constructor co-allocates both
(80 B, 1 alloc). Net −13 lines.

TsconfigChange allocs −4.8%, B/op −1%; InitialLoad retained −2 MB.

Andrew Branch (andrewbranch) · 2026-10-19T19:13:35Z

TypeScript Bot (@typescript-bot) perf test this

typescript-automation · 2026-10-19T19:13:42Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`perf test this`	✅ Started	👀 Results

typescript-automation · 2026-10-19T19:46:37Z

Andrew Branch (@andrewbranch)
The results of the perf run you requested are in!

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_115,276	_115,276	_~	_~	_~	_{p=1.000 n=12}
_Types	_79,613	_79,613	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{113,591k (± 0.05%)}	_{113,606k (± 0.06%)}	_~	_113,452k	_113,759k	_{p=0.660 n=12}
_{Memory Allocs}	_{2,212,531 (± 0.01%)}	_{2,212,213 (± 0.01%)}	_{-318 (- 0.01%)}	_2,211,984	_2,212,601	_{p=0.001 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.049s (± 3.78%)}	_{0.049s (± 2.36%)}	_~	_0.045s	_0.051s	_{p=0.920 n=12}
_{Bind Time}	_{0.018s (± 8.26%)}	_{0.017s (± 8.52%)}	_~	_0.014s	_0.022s	_{p=0.135 n=12}
_{Check Time}	_{0.562s (± 1.04%)}	_{0.559s (± 0.99%)}	_~	_0.550s	_0.579s	_{p=0.096 n=12}
_{Emit Time}	_{0.328s (± 2.17%)}	_{0.322s (± 2.24%)}	_~	_0.309s	_0.342s	_{p=0.213 n=12}
_{Total Time}	_{0.965s (± 0.80%)}	_{0.955s (± 0.74%)}	_~	_0.937s	_0.973s	_{p=0.057 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{846,983 (± 0.06%)}	_{846,942 (± 0.04%)}	_~	_846,110	_848,011	_{p=0.977 n=12}
_Types	_{247,031 (± 0.00%)}	_{247,031 (± 0.00%)}	_~	_247,030	_247,033	_{p=0.982 n=12}
_{Memory Used}	_{596,501k (± 0.04%)}	_{596,189k (± 0.03%)}	_{-313k (- 0.05%)}	_595,847k	_596,751k	_{p=0.028 n=12}
_{Memory Allocs}	_{13,141,800 (± 0.04%)}	_{13,078,059 (± 0.07%)}	_{-63,742 (- 0.49%)}	_13,066,562	_13,111,453	_{p=0.000 n=12}
_{Config Time}	_0.020s	_0.015s	_{🟩-0.005s (-25.00%)}	_~	_~	_{p=0.000 n=12}
_{Parse Time}	_{0.282s (± 1.83%)}	_{0.290s (± 2.15%)}	_{+0.008s (+ 2.75%)}	_0.272s	_0.310s	_{p=0.046 n=12}
_{Bind Time}	_{0.102s (±10.03%)}	_{0.081s (± 6.83%)}	_{🟩-0.021s (-20.79%)}	_0.071s	_0.097s	_{p=0.002 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.860s (± 1.54%)}	_{1.879s (± 1.65%)}	_~	_1.784s	_1.923s	_{p=0.164 n=12}
_{Total Time}	_{2.288s (± 1.34%)}	_{2.282s (± 1.47%)}	_~	_2.183s	_2.343s	_{p=0.843 n=12}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_4,331,983	_4,331,983	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,370,520	_1,370,520	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{2,625,492k (± 0.06%)}	_{2,624,302k (± 0.07%)}	_~	_2,620,262k	_2,628,363k	_{p=0.443 n=12}
_{Memory Allocs}	_{27,694,010 (± 0.07%)}	_{27,439,831 (± 0.07%)}	_{-254,179 (- 0.92%)}	_27,385,334	_27,502,889	_{p=0.000 n=12}
_{Config Time}	_{0.020s (± 0.90%)}	_0.015s	_{🟩-0.005s (-25.31%)}	_~	_~	_{p=0.000 n=12}
_{Parse Time}	_{0.580s (± 3.00%)}	_{0.558s (± 3.05%)}	_~	_0.511s	_0.593s	_{p=0.060 n=12}
_{Bind Time}	_{0.003s (±24.75%)}	_{0.003s (±24.75%)}	_~	_0.002s	_0.006s	_{p=1.000 n=12}
_{Check Time}	_{8.658s (± 0.28%)}	_{8.565s (± 0.34%)}	_{-0.093s (- 1.07%)}	_8.518s	_8.689s	_{p=0.000 n=12}
_{Emit Time}	_{0.706s (±10.82%)}	_{0.595s (±13.32%)}	_{🟩-0.111s (-15.69%)}	_0.498s	_0.801s	_{p=0.027 n=12}
_{Total Time}	_{10.901s (± 0.52%)}	_{10.620s (± 1.03%)}	_{-0.281s (- 2.58%)}	_10.416s	_10.856s	_{p=0.000 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,388,680	_1,388,680	_~	_~	_~	_{p=1.000 n=12}
_Types	_441,862	_441,862	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,312,862k (± 0.64%)}	_{1,316,123k (± 0.70%)}	_~	_1,296,678k	_1,336,647k	_{p=0.443 n=12}
_{Memory Allocs}	_{78,130,520 (± 0.14%)}	_{77,907,481 (± 0.09%)}	_{-223,039 (- 0.29%)}	_77,603,392	_78,084,042	_{p=0.004 n=12}
_{Config Time}	_{0.005s (±11.96%)}	_{0.007s (± 9.00%)}	_{🔻+0.002s (+44.64%)}	_0.005s	_0.008s	_{p=0.000 n=12}
_{Parse Time}	_{0.311s (± 2.04%)}	_{0.302s (± 2.21%)}	_~	_0.286s	_0.320s	_{p=0.081 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{2.005s (± 0.48%)}	_{2.010s (± 0.42%)}	_~	_1.991s	_2.036s	_{p=0.325 n=12}
_{Emit Time}	_{0.359s (± 4.50%)}	_{0.345s (± 4.33%)}	_~	_0.302s	_0.389s	_{p=0.311 n=12}
_{Total Time}	_{23.910s (± 0.68%)}	_{23.690s (± 0.66%)}	_{-0.220s (- 0.92%)}	_23.156s	_23.976s	_{p=0.045 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_334,953	_334,953	_~	_~	_~	_{p=1.000 n=12}
_Types	_197,616	_197,616	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{247,540k (± 0.03%)}	_{247,488k (± 0.03%)}	_~	_247,245k	_247,669k	_{p=0.111 n=12}
_{Memory Allocs}	_{4,329,822 (± 0.01%)}	_{4,326,464 (± 0.01%)}	_{-3,358 (- 0.08%)}	_4,325,511	_4,327,582	_{p=0.000 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.112s (± 4.75%)}	_{0.116s (± 4.45%)}	_~	_0.100s	_0.124s	_{p=0.172 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{0.954s (± 0.45%)}	_{0.957s (± 0.56%)}	_~	_0.945s	_0.973s	_{p=0.503 n=12}
_{Emit Time}	_{0.156s (± 3.77%)}	_{0.148s (± 5.88%)}	_~	_0.129s	_0.173s	_{p=0.164 n=12}
_{Total Time}	_{1.278s (± 0.58%)}	_{1.277s (± 0.93%)}	_~	_1.246s	_1.304s	_{p=0.943 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_303,834	_303,834	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,663	_181,663	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{215,260k (± 0.02%)}	_{215,234k (± 0.01%)}	_~	_215,162k	_215,324k	_{p=0.291 n=12}
_{Memory Allocs}	_{1,401,676 (± 0.02%)}	_{1,401,236 (± 0.01%)}	_{-439 (- 0.03%)}	_1,400,774	_1,401,743	_{p=0.006 n=12}
_{Config Time}	_0.000s	_{0.000s (±217.90%)}	_~	_0.000s	_0.001s	_{p=1.000 n=12}
_{Parse Time}	_{0.097s (± 3.53%)}	_{0.096s (± 5.19%)}	_~	_0.088s	_0.111s	_{p=0.450 n=12}
_{Bind Time}	_{0.040s (±11.70%)}	_{0.040s (± 9.88%)}	_~	_0.030s	_0.048s	_{p=0.701 n=12}
_{Check Time}	_{0.745s (± 0.94%)}	_{0.743s (± 1.02%)}	_~	_0.726s	_0.762s	_{p=0.681 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.897s (± 0.76%)}	_{0.895s (± 0.96%)}	_~	_0.877s	_0.926s	_{p=0.766 n=12}
_{vscode - native}
_Errors	₃₉₆	₃₉₆	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_12,483,880	_12,483,880	_~	_~	_~	_{p=1.000 n=12}
_Types	_4,085,331	_4,085,331	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,845,353k (± 0.03%)}	_{5,843,014k (± 0.01%)}	_{-2,339k (- 0.04%)}	_5,840,755k	_5,844,615k	_{p=0.006 n=12}
_{Memory Allocs}	_{59,433,051 (± 0.02%)}	_{58,315,740 (± 0.01%)}	_{-1,117,310 (- 1.88%)}	_58,306,315	_58,334,956	_{p=0.000 n=12}
_{Config Time}	_{0.076s (± 0.41%)}	_{0.049s (± 0.66%)}	_{🟩-0.027s (-35.15%)}	_0.049s	_0.050s	_{p=0.000 n=12}
_{Parse Time}	_{1.816s (± 1.93%)}	_{1.825s (± 2.42%)}	_~	_1.691s	_1.944s	_{p=0.799 n=12}
_{Bind Time}	_{0.717s (±14.97%)}	_{0.594s (±14.70%)}	_{🟩-0.123s (-17.19%)}	_0.503s	_0.954s	_{p=0.024 n=12}
_{Check Time}	_{15.749s (± 1.09%)}	_{15.911s (± 0.98%)}	_~	_15.443s	_16.158s	_{p=0.236 n=12}
_{Emit Time}	_{5.809s (± 6.98%)}	_{5.454s (± 4.56%)}	_~	_4.875s	_6.361s	_{p=0.128 n=12}
_{Total Time}	_{24.259s (± 1.25%)}	_{23.917s (± 0.67%)}	_{-0.342s (- 1.41%)}	_23.585s	_24.600s	_{p=0.039 n=12}
_{webpack - native}
_Errors	₅₉₈	₅₉₈	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,343,495	_1,343,495	_~	_~	_~	_{p=1.000 n=12}
_Types	_651,492	_651,492	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{855,319k (± 0.01%)}	_{855,121k (± 0.02%)}	_{-198k (- 0.02%)}	_854,687k	_855,444k	_{p=0.039 n=12}
_{Memory Allocs}	_{6,770,093 (± 0.01%)}	_{6,724,154 (± 0.02%)}	_{-45,939 (- 0.68%)}	_6,720,654	_6,730,113	_{p=0.000 n=12}
_{Config Time}	_{0.008s (± 4.38%)}	_{0.006s (± 2.98%)}	_{🟩-0.001s (-18.89%)}	_0.006s	_0.007s	_{p=0.000 n=12}
_{Parse Time}	_{0.239s (± 3.29%)}	_{0.236s (± 4.35%)}	_~	_0.212s	_0.270s	_{p=0.541 n=12}
_{Bind Time}	_{0.062s (±12.73%)}	_{0.077s (±18.28%)}	_~	_0.054s	_0.109s	_{p=0.070 n=12}
_{Check Time}	_{2.324s (± 0.50%)}	_{2.269s (± 0.70%)}	_{-0.054s (- 2.35%)}	_2.228s	_2.299s	_{p=0.000 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{2.664s (± 0.33%)}	_{2.619s (± 0.44%)}	_{-0.045s (- 1.68%)}	_2.583s	_2.639s	_{p=0.000 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,060,810	_1,060,810	_~	_~	_~	_{p=1.000 n=12}
_Types	_389,671	_389,671	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{471,799k (± 0.02%)}	_{471,755k (± 0.03%)}	_~	_471,531k	_472,243k	_{p=0.377 n=12}
_{Memory Allocs}	_{4,216,884 (± 0.11%)}	_{4,191,660 (± 0.16%)}	_{-25,224 (- 0.60%)}	_4,175,456	_4,218,103	_{p=0.000 n=12}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.109s (± 2.96%)}	_{0.107s (± 2.74%)}	_~	_0.103s	_0.118s	_{p=0.464 n=12}
_{Bind Time}	_{0.035s (±17.20%)}	_{0.035s (±18.46%)}	_~	_0.026s	_0.056s	_{p=0.719 n=12}
_{Check Time}	_{0.907s (± 1.25%)}	_{0.906s (± 1.01%)}	_~	_0.887s	_0.933s	_{p=0.876 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.059s (± 1.17%)}	_{1.057s (± 0.89%)}	_~	_1.026s	_1.081s	_{p=0.899 n=12}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
mui-docs - native
strada-build-src - native
strada-compiler - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

lsp

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-UnionsLSP - native}
_{Req 1 - updateOpen}	_{11ms (±20.59%)}	_{12ms (±12.45%)}	_~	_9ms	_15ms	_{p=0.056 n=12}
_{Req 2 - geterr}	_{541ms (± 0.36%)}	_{535ms (± 0.28%)}	_{-6ms (- 1.06%)}	_532ms	_539ms	_{p=0.000 n=12}
_{Req 3 - references}	_{44ms (± 4.33%)}	_{47ms (± 4.01%)}	_{🔻+2ms (+ 5.08%)}	_43ms	_51ms	_{p=0.028 n=12}
_{Req 4 - navto}	_{16ms (± 1.90%)}	_{17ms (± 5.69%)}	_~	_16ms	_21ms	_{p=0.369 n=12}
_{Req 5 - completionInfo count}	_1,363	_1,363	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{16ms (± 7.93%)}	_{16ms (± 8.87%)}	_~	_14ms	_21ms	_{p=0.304 n=12}
_{CompilerLSP - native}
_{Req 1 - updateOpen}	_{13ms (±13.31%)}	_{11ms (±13.99%)}	_~	_10ms	_17ms	_{p=0.440 n=12}
_{Req 2 - geterr}	_{284ms (± 0.67%)}	_{285ms (± 0.48%)}	_~	_281ms	_288ms	_{p=0.940 n=12}
_{Req 3 - references}	_{49ms (± 1.17%)}	_{49ms (± 1.44%)}	_~	_48ms	_51ms	_{p=0.760 n=12}
_{Req 4 - navto}	_{19ms (± 8.20%)}	_{18ms (± 6.17%)}	_~	_17ms	_22ms	_{p=0.139 n=12}
_{Req 5 - completionInfo count}	_1,525	_1,525	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{20ms (±11.45%)}	_{20ms (±11.60%)}	_~	_15ms	_24ms	_{p=0.725 n=12}

System info unknown

Hosts

native

Scenarios

CompilerLSP - native
Compiler-UnionsLSP - native
xstate-main-1-LSP - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{lsp-startup - native}
_{Execution time}	_{4.66ms (±365.09%)}	_{4.67ms (±365.09%)}	_{+0.01ms (+ 0.25%)}	_0.00ms	_472.63ms	_{p=0.000 n=1200}
_{tsgo-startup - native}
_{Execution time}	_{5.67ms (±365.09%)}	_{5.68ms (±365.09%)}	_{+0.01ms (+ 0.20%)}	_0.00ms	_572.39ms	_{p=0.000 n=1200}

System info unknown

Hosts

native

Scenarios

lsp-startup - native
tsgo-startup - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

Download Benchmarks

Copilot

🔵 Needs a closer look

Concurrent filesystem traversal and compiler-wide representation changes warrant human review, particularly without executed validation.

No open issues 🎉

1 resolved since last review

Single-threaded mode still performs concurrent directory reads

_{Review effort: Balanced}

Andrew Branch (andrewbranch) · 2026-10-19T21:21:10Z

TypeScript Bot (@typescript-bot) perf test

typescript-automation · 2026-10-19T21:21:16Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`perf test`	✅ Started	👀 Results

typescript-automation · 2026-10-19T21:52:41Z

Andrew Branch (@andrewbranch)
The results of the perf run you requested are in!

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_115,276	_115,276	_~	_~	_~	_{p=1.000 n=12}
_Types	_79,613	_79,613	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{113,527k (± 0.07%)}	_{113,538k (± 0.07%)}	_~	_113,376k	_113,791k	_{p=0.887 n=12}
_{Memory Allocs}	_{2,212,615 (± 0.01%)}	_{2,212,232 (± 0.01%)}	_{-383 (- 0.02%)}	_2,211,899	_2,212,916	_{p=0.001 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.049s (± 3.28%)}	_{0.048s (± 3.43%)}	_~	_0.045s	_0.055s	_{p=0.659 n=12}
_{Bind Time}	_{0.017s (±10.21%)}	_{0.017s (± 8.41%)}	_~	_0.013s	_0.020s	_{p=0.639 n=12}
_{Check Time}	_{0.561s (± 0.56%)}	_{0.558s (± 0.71%)}	_~	_0.550s	_0.568s	_{p=0.172 n=12}
_{Emit Time}	_{0.328s (± 2.74%)}	_{0.324s (± 1.98%)}	_~	_0.303s	_0.338s	_{p=0.680 n=12}
_{Total Time}	_{0.963s (± 1.03%)}	_{0.955s (± 0.95%)}	_~	_0.931s	_0.977s	_{p=0.486 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{846,989 (± 0.06%)}	_{846,907 (± 0.08%)}	_~	_845,756	_848,830	_{p=0.630 n=12}
_Types	_{247,031 (± 0.00%)}	_{247,032 (± 0.00%)}	_~	_247,030	_247,044	_{p=0.536 n=12}
_{Memory Used}	_{596,350k (± 0.02%)}	_{596,208k (± 0.03%)}	_~	_595,800k	_596,572k	_{p=0.178 n=12}
_{Memory Allocs}	_{13,138,240 (± 0.01%)}	_{13,074,668 (± 0.05%)}	_{-63,571 (- 0.48%)}	_13,065,745	_13,095,793	_{p=0.000 n=12}
_{Config Time}	_{0.020s (± 1.21%)}	_{0.015s (± 1.20%)}	_{🟩-0.005s (-25.21%)}	_0.015s	_0.016s	_{p=0.000 n=12}
_{Parse Time}	_{0.279s (± 1.87%)}	_{0.287s (± 2.65%)}	_~	_0.274s	_0.314s	_{p=0.109 n=12}
_{Bind Time}	_{0.102s (±15.67%)}	_{0.077s (± 4.75%)}	_{🟩-0.024s (-23.96%)}	_0.068s	_0.089s	_{p=0.008 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.878s (± 1.59%)}	_{1.874s (± 1.69%)}	_~	_1.803s	_1.950s	_{p=0.855 n=12}
_{Total Time}	_{2.298s (± 1.18%)}	_{2.269s (± 1.40%)}	_~	_2.202s	_2.352s	_{p=0.291 n=12}
_{arktype - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,757,463	_1,757,463	_~	_~	_~	_{p=1.000 n=12}
_Types	_943,966	_943,966	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{703,690k (± 0.01%)}	_{703,618k (± 0.01%)}	_~	_703,517k	_703,856k	_{p=0.091 n=12}
_{Memory Allocs}	_{13,293,129 (± 0.02%)}	_{13,275,828 (± 0.01%)}	_{-17,301 (- 0.13%)}	_13,273,723	_13,278,395	_{p=0.000 n=12}
_{Config Time}	_0.003s	_{0.002s (±12.64%)}	_{🟩-0.001s (-25.00%)}	_0.002s	_0.003s	_{p=0.000 n=12}
_{Parse Time}	_{0.091s (± 3.94%)}	_{0.086s (± 3.19%)}	_{🟩-0.005s (- 5.65%)}	_0.080s	_0.095s	_{p=0.023 n=12}
_{Bind Time}	_{0.027s (±13.06%)}	_{0.027s (±10.60%)}	_~	_0.024s	_0.036s	_{p=1.000 n=12}
_{Check Time}	_{2.450s (± 0.30%)}	_{2.439s (± 0.39%)}	_~	_2.411s	_2.463s	_{p=0.071 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{2.623s (± 0.41%)}	_{2.607s (± 0.36%)}	_{-0.016s (- 0.63%)}	_2.577s	_2.630s	_{p=0.045 n=12}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_4,331,983	_4,331,983	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,370,520	_1,370,520	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{2,625,122k (± 0.05%)}	_{2,624,401k (± 0.07%)}	_~	_2,620,409k	_2,628,701k	_{p=0.551 n=12}
_{Memory Allocs}	_{27,702,105 (± 0.06%)}	_{27,433,011 (± 0.05%)}	_{-269,094 (- 0.97%)}	_27,401,450	_27,465,329	_{p=0.000 n=12}
_{Config Time}	_{0.020s (± 1.52%)}	_{0.015s (± 1.61%)}	_{🟩-0.005s (-25.41%)}	_0.015s	_0.016s	_{p=0.000 n=12}
_{Parse Time}	_{0.590s (± 3.07%)}	_{0.550s (± 3.42%)}	_{🟩-0.040s (- 6.82%)}	_0.511s	_0.597s	_{p=0.005 n=12}
_{Bind Time}	_{0.002s (±13.40%)}	_{0.003s (±12.54%)}	_~	_0.002s	_0.003s	_{p=0.684 n=12}
_{Check Time}	_{8.637s (± 0.13%)}	_{8.526s (± 0.56%)}	_{-0.110s (- 1.28%)}	_8.384s	_8.717s	_{p=0.000 n=12}
_{Emit Time}	_{0.725s (±10.10%)}	_{0.661s (±13.47%)}	_~	_0.499s	_0.800s	_{p=1.000 n=12}
_{Total Time}	_{10.886s (± 0.74%)}	_{10.652s (± 0.98%)}	_{-0.235s (- 2.15%)}	_10.432s	_10.825s	_{p=0.000 n=12}
_{sentry - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_7,459,653	_7,459,653	_~	_~	_~	_{p=1.000 n=12}
_Types	_2,647,172	_2,647,172	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{3,803,448k (± 0.03%)}	_{3,801,312k (± 0.03%)}	_{-2,136k (- 0.06%)}	_3,799,112k	_3,804,847k	_{p=0.006 n=12}
_{Memory Allocs}	_{77,165,486 (± 0.08%)}	_{76,682,925 (± 0.06%)}	_{-482,561 (- 0.63%)}	_76,569,505	_76,806,352	_{p=0.000 n=12}
_{Config Time}	_{0.060s (± 0.51%)}	_{0.041s (± 0.69%)}	_{🟩-0.019s (-31.63%)}	_0.041s	_0.042s	_{p=0.000 n=12}
_{Parse Time}	_{1.033s (± 3.80%)}	_{0.994s (± 2.01%)}	_~	_0.931s	_1.034s	_{p=0.091 n=12}
_{Bind Time}	_{0.308s (±12.10%)}	_{0.286s (±11.98%)}	_~	_0.255s	_0.418s	_{p=0.171 n=12}
_{Check Time}	_{14.777s (± 0.51%)}	_{14.582s (± 0.19%)}	_{-0.196s (- 1.32%)}	_14.509s	_14.635s	_{p=0.000 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{16.251s (± 0.45%)}	_{15.970s (± 0.17%)}	_{-0.281s (- 1.73%)}	_15.883s	_16.024s	_{p=0.000 n=12}
_{social-app - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_2,568,629	_2,568,629	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,163,035	_1,163,035	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,212,943k (± 0.01%)}	_{1,212,506k (± 0.01%)}	_{-437k (- 0.04%)}	_1,211,908k	_1,212,922k	_{p=0.000 n=12}
_{Memory Allocs}	_{13,987,652 (± 0.17%)}	_{13,885,118 (± 0.42%)}	_{-102,534 (- 0.73%)}	_13,819,844	_14,156,480	_{p=0.000 n=12}
_{Config Time}	_{0.017s (± 1.65%)}	_{0.013s (± 2.45%)}	_{🟩-0.005s (-26.57%)}	_0.012s	_0.013s	_{p=0.000 n=12}
_{Parse Time}	_{0.357s (± 1.24%)}	_{0.341s (± 2.23%)}	_{🟩-0.015s (- 4.28%)}	_0.328s	_0.371s	_{p=0.001 n=12}
_{Bind Time}	_{0.079s (±10.12%)}	_{0.086s (±15.80%)}	_~	_0.068s	_0.129s	_{p=0.382 n=12}
_{Check Time}	_{3.647s (± 0.26%)}	_{3.615s (± 0.33%)}	_{-0.033s (- 0.90%)}	_3.578s	_3.639s	_{p=0.000 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{4.122s (± 0.40%)}	_{4.078s (± 0.46%)}	_{-0.044s (- 1.07%)}	_4.030s	_4.127s	_{p=0.001 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,388,680	_1,388,680	_~	_~	_~	_{p=1.000 n=12}
_Types	_441,862	_441,862	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,312,483k (± 0.57%)}	_{1,315,779k (± 0.35%)}	_~	_1,305,802k	_1,331,129k	_{p=0.319 n=12}
_{Memory Allocs}	_{78,202,041 (± 0.13%)}	_{77,890,688 (± 0.11%)}	_{-311,353 (- 0.40%)}	_77,574,236	_78,104,482	_{p=0.000 n=12}
_{Config Time}	_{0.005s (± 8.27%)}	_{0.005s (±13.27%)}	_~	_0.004s	_0.007s	_{p=0.152 n=12}
_{Parse Time}	_{0.308s (± 1.73%)}	_{0.303s (± 2.34%)}	_~	_0.287s	_0.321s	_{p=0.311 n=12}
_{Bind Time}	_{0.000s (±217.90%)}	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{2.012s (± 0.62%)}	_{2.000s (± 0.41%)}	_~	_1.981s	_2.020s	_{p=0.091 n=12}
_{Emit Time}	_{0.348s (± 4.09%)}	_{0.341s (± 4.09%)}	_~	_0.314s	_0.387s	_{p=0.418 n=12}
_{Total Time}	_{23.880s (± 0.50%)}	_{23.596s (± 0.69%)}	_{-0.284s (- 1.19%)}	_23.230s	_23.973s	_{p=0.010 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_334,953	_334,953	_~	_~	_~	_{p=1.000 n=12}
_Types	_197,616	_197,616	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{247,490k (± 0.03%)}	_{247,433k (± 0.02%)}	_~	_247,298k	_247,526k	_{p=0.068 n=12}
_{Memory Allocs}	_{4,329,511 (± 0.01%)}	_{4,325,973 (± 0.01%)}	_{-3,538 (- 0.08%)}	_4,324,662	_4,326,755	_{p=0.000 n=12}
_{Config Time}	_{0.001s (±37.93%)}	_{0.000s (±77.74%)}	_~	_0.000s	_0.001s	_{p=0.214 n=12}
_{Parse Time}	_{0.090s (± 4.63%)}	_{0.095s (± 4.22%)}	_~	_0.084s	_0.107s	_{p=0.057 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{0.798s (± 0.76%)}	_{0.793s (± 0.70%)}	_~	_0.784s	_0.815s	_{p=0.202 n=12}
_{Emit Time}	_{0.124s (± 4.53%)}	_{0.128s (± 3.42%)}	_~	_0.116s	_0.139s	_{p=0.323 n=12}
_{Total Time}	_{1.056s (± 0.51%)}	_{1.063s (± 0.64%)}	_~	_1.039s	_1.080s	_{p=0.070 n=12}
_{t3code-server - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_11,588,087	_11,588,087	_~	_~	_~	_{p=1.000 n=12}
_Types	_3,062,556	_3,062,556	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{3,946,543k (± 0.01%)}	_{3,944,580k (± 0.01%)}	_{-1,964k (- 0.05%)}	_3,943,226k	_3,946,342k	_{p=0.000 n=12}
_{Memory Allocs}	_{41,547,231 (± 0.06%)}	_{41,381,098 (± 0.04%)}	_{-166,133 (- 0.40%)}	_41,345,948	_41,423,159	_{p=0.000 n=12}
_{Config Time}	_0.006s	_{0.005s (± 3.57%)}	_{🟩-0.001s (-15.28%)}	_0.005s	_0.006s	_{p=0.000 n=12}
_{Parse Time}	_{0.570s (± 2.52%)}	_{0.549s (± 1.99%)}	_~	_0.529s	_0.597s	_{p=0.071 n=12}
_{Bind Time}	_{0.181s (±16.62%)}	_{0.196s (±10.08%)}	_~	_0.153s	_0.244s	_{p=0.074 n=12}
_{Check Time}	_{18.663s (± 0.39%)}	_{18.592s (± 0.46%)}	_{-0.071s (- 0.38%)}	_18.447s	_18.923s	_{p=0.045 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{19.435s (± 0.38%)}	_{19.364s (± 0.43%)}	_~	_19.241s	_19.713s	_{p=0.066 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_303,834	_303,834	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,663	_181,663	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{215,235k (± 0.02%)}	_{215,252k (± 0.01%)}	_~	_215,171k	_215,313k	_{p=0.504 n=12}
_{Memory Allocs}	_{1,401,665 (± 0.02%)}	_{1,401,192 (± 0.02%)}	_{-472 (- 0.03%)}	_1,400,416	_1,401,892	_{p=0.014 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.079s (± 3.93%)}	_{0.079s (± 5.04%)}	_~	_0.069s	_0.088s	_{p=0.921 n=12}
_{Bind Time}	_{0.033s (±10.26%)}	_{0.033s (± 8.87%)}	_~	_0.024s	_0.040s	_{p=0.921 n=12}
_{Check Time}	_{0.618s (± 1.19%)}	_{0.613s (± 0.99%)}	_~	_0.603s	_0.631s	_{p=0.433 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.743s (± 0.93%)}	_{0.738s (± 0.83%)}	_~	_0.719s	_0.751s	_{p=0.504 n=12}
_{vscode - native}
_Errors	₃₉₆	₃₉₆	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_12,489,159	_12,489,159	_~	_~	_~	_{p=1.000 n=12}
_Types	_4,083,411	_4,083,411	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,851,727k (± 0.03%)}	_{5,849,628k (± 0.01%)}	_{-2,099k (- 0.04%)}	_5,846,813k	_5,851,034k	_{p=0.020 n=12}
_{Memory Allocs}	_{59,515,692 (± 0.04%)}	_{58,399,500 (± 0.01%)}	_{-1,116,191 (- 1.88%)}	_58,386,594	_58,418,313	_{p=0.000 n=12}
_{Config Time}	_{0.062s (± 0.50%)}	_{0.040s (± 1.81%)}	_{🟩-0.022s (-35.03%)}	_0.040s	_0.044s	_{p=0.000 n=12}
_{Parse Time}	_{1.448s (± 2.72%)}	_{1.456s (± 2.21%)}	_~	_1.384s	_1.528s	_{p=0.630 n=12}
_{Bind Time}	_{0.631s (±11.98%)}	_{0.479s (± 9.59%)}	_{🟩-0.152s (-24.04%)}	_0.409s	_0.625s	_{p=0.003 n=12}
_{Check Time}	_{13.637s (± 1.13%)}	_{13.652s (± 1.10%)}	_~	_13.352s	_13.947s	_{p=0.590 n=12}
_{Emit Time}	_{4.662s (± 5.30%)}	_{4.824s (± 6.76%)}	_~	_4.207s	_5.533s	_{p=0.551 n=12}
_{Total Time}	_{20.522s (± 0.81%)}	_{20.526s (± 0.97%)}	_~	_20.167s	_21.028s	_{p=0.755 n=12}
_{webpack - native}
_Errors	₅₉₈	₅₉₈	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,343,495	_1,343,495	_~	_~	_~	_{p=1.000 n=12}
_Types	_651,492	_651,492	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{855,379k (± 0.01%)}	_{855,138k (± 0.02%)}	_{-241k (- 0.03%)}	_854,686k	_855,431k	_{p=0.006 n=12}
_{Memory Allocs}	_{6,768,818 (± 0.01%)}	_{6,730,140 (± 0.16%)}	_{-38,678 (- 0.57%)}	_6,720,048	_6,772,058	_{p=0.000 n=12}
_{Config Time}	_0.009s	_0.008s	_{🟩-0.001s (-11.11%)}	_~	_~	_{p=0.000 n=12}
_{Parse Time}	_{0.319s (± 2.46%)}	_{0.298s (± 3.43%)}	_{🟩-0.021s (- 6.54%)}	_0.267s	_0.329s	_{p=0.004 n=12}
_{Bind Time}	_{0.075s (± 8.20%)}	_{0.094s (±17.94%)}	_~	_0.069s	_0.141s	_{p=0.065 n=12}
_{Check Time}	_{2.773s (± 0.48%)}	_{2.714s (± 0.79%)}	_{-0.059s (- 2.14%)}	_2.670s	_2.767s	_{p=0.000 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{3.212s (± 0.43%)}	_{3.150s (± 0.47%)}	_{-0.063s (- 1.95%)}	_3.110s	_3.191s	_{p=0.000 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,060,810	_1,060,810	_~	_~	_~	_{p=1.000 n=12}
_Types	_389,671	_389,671	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{471,862k (± 0.02%)}	_{471,798k (± 0.04%)}	_~	_471,451k	_472,393k	_{p=0.266 n=12}
_{Memory Allocs}	_{4,223,145 (± 0.08%)}	_{4,188,389 (± 0.11%)}	_{-34,756 (- 0.82%)}	_4,174,846	_4,204,036	_{p=0.000 n=12}
_{Config Time}	_0.003s	_0.002s	_{🟩-0.001s (-33.33%)}	_~	_~	_{p=0.000 n=12}
_{Parse Time}	_{0.134s (± 3.69%)}	_{0.135s (± 3.15%)}	_~	_0.125s	_0.149s	_{p=0.504 n=12}
_{Bind Time}	_{0.051s (±13.15%)}	_{0.048s (±14.59%)}	_~	_0.035s	_0.069s	_{p=0.522 n=12}
_{Check Time}	_{1.089s (± 0.76%)}	_{1.087s (± 1.01%)}	_~	_1.065s	_1.123s	_{p=0.258 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.285s (± 0.69%)}	_{1.279s (± 0.89%)}	_~	_1.248s	_1.305s	_{p=0.451 n=12}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
arktype - native
mui-docs - native
sentry - native
social-app - native
strada-build-src - native
strada-compiler - native
t3code-server - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

lsp

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-UnionsLSP - native}
_{Req 1 - updateOpen}	_{10ms (±13.94%)}	_{12ms (±15.38%)}	_~	_9ms	_17ms	_{p=0.218 n=12}
_{Req 2 - geterr}	_{540ms (± 0.33%)}	_{535ms (± 0.36%)}	_{-6ms (- 1.09%)}	_529ms	_539ms	_{p=0.000 n=12}
_{Req 3 - references}	_{45ms (± 4.26%)}	_{47ms (± 5.29%)}	_~	_39ms	_50ms	_{p=0.202 n=12}
_{Req 4 - navto}	_{16ms (± 1.90%)}	_{17ms (± 1.99%)}	_~	_16ms	_17ms	_{p=0.680 n=12}
_{Req 5 - completionInfo count}	_1,363	_1,363	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{15ms (± 5.26%)}	_{16ms (± 6.17%)}	_~	_14ms	_19ms	_{p=0.522 n=12}
_{CompilerLSP - native}
_{Req 1 - updateOpen}	_{12ms (±16.30%)}	_{10ms (± 1.80%)}	_~	_10ms	_11ms	_{p=0.223 n=12}
_{Req 2 - geterr}	_{283ms (± 0.32%)}	_{284ms (± 0.66%)}	_~	_280ms	_288ms	_{p=0.280 n=12}
_{Req 3 - references}	_{48ms (± 2.25%)}	_{48ms (± 1.35%)}	_~	_45ms	_49ms	_{p=0.417 n=12}
_{Req 4 - navto}	_{17ms (± 1.43%)}	_{18ms (± 6.75%)}	_~	_17ms	_22ms	_{p=0.112 n=12}
_{Req 5 - completionInfo count}	_1,525	_1,525	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{22ms (± 5.76%)}	_{20ms (±11.11%)}	_~	_15ms	_23ms	_{p=0.106 n=12}

System info unknown

Hosts

native

Scenarios

CompilerLSP - native
Compiler-UnionsLSP - native
xstate-main-1-LSP - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{lsp-startup - native}
_{Execution time}	_{4.64ms (±365.09%)}	_{4.66ms (±365.08%)}	_{+0.02ms (+ 0.38%)}	_0.00ms	_468.21ms	_{p=0.000 n=1200}
_{tsgo-startup - native}
_{Execution time}	_{5.69ms (±365.09%)}	_{5.72ms (±365.10%)}	_{+0.03ms (+ 0.50%)}	_0.00ms	_580.57ms	_{p=0.020 n=1200}

System info unknown

Hosts

native

Scenarios

lsp-startup - native
tsgo-startup - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

Download Benchmarks

dirty.SyncMap.Load allocates an entry wrapper on every hit in the base map. snapshotFSBuilder reads only need the value, so add LoadClean, which returns base values without allocating when the key is not dirty. Perf (vscode, unpinned; indicative): EditImports -4.7% allocs; CreateDeleteFile -4.6% allocs, -1.9% B/op. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

parseTask is allocated for every file reference edge, but most edges point at files that are already loaded. Moving load results into a side record and removing two unused fields shrinks parseTask from 368B to 184B. Perf (vscode, unpinned; indicative): EditImports and CreateDeleteFile -7.4% B/op, +0.3% allocs; time within noise. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

Config file-name expansion read the include tree with sequential ReadDir calls. A core.WorkGroup limited to GOMAXPROCS now reads the same directories first (honoring excludes and depth), then the unchanged ordered walk runs over the prefetched entries, so results and ordering are identical. Directories under overlapping base paths are read once. Symlinked directories are left to the ordered walk, which owns realpath deduplication; each directory spelling is read at most once by the prefetch. A host panic stops further reads and is re-raised on the caller. With --singleThreaded, config expansion reads directories serially. Perf (ReadDirectory over vscode@9c4bcec0bb91/src with osvfs, machine under load; indicative): 193 -> 52 ms (-73%); transient +25% B/op, +22% allocs/op for queued closures and goroutines. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

…files Also return host directory entries directly from overlayFS when no overlay directory affects them. Perf (vscode, unpinned; indicative): program-rebuild benchmarks -2-3% allocs, -2% B/op. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

ReuseProgram clones the package.json info cache on every edit; copying a sync.Map entry-by-entry allocated per entry. Reads now hit an immutable base map without locking, new entries go to a sync.Map overlay (first writer wins), and Clone flattens both into a new base. Perf (vscode, unpinned; indicative): WatchChange -90% allocs; EditImports and EditOpenFile time not regressed (an RWMutex variant regressed EditImports +38% from read-lock contention). Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

Store ModuleID's path/specifier in a single string (only one is ever set), narrow ExportSyntax and ScriptElementKind to uint8, and reorder small fields to avoid padding. Perf (vscode, unpinned; indicative): AutoImportInitial retained memory -15.7% (19.8 -> 16.7 MB); time and allocs unchanged. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

Perf (vscode, unpinned; indicative): TsconfigChange and CreateDeleteFile -2.1% B/op, -1.8% allocs. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

Perf (vscode, unpinned; indicative): TsconfigChange -12.8% B/op, -13.2% allocs; InitialLoad -5% allocs. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

…tring Perf (vscode, unpinned; indicative): TsconfigChange -12.1% B/op, -12.9% allocs; InitialLoad -4.8% allocs. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

…tes) Perf (vscode, unpinned; indicative): TsconfigChange -3.8% B/op; allocs unchanged. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

… 80B/1) Perf (vscode, unpinned; indicative): TsconfigChange -4.8% allocs, -1% B/op; InitialLoad retained memory -2 MB. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: afcfca01-a049-4749-ad08-1c00c586f6a1

Andrew Branch (andrewbranch) · 2026-11-05T18:55:03Z

TypeScript Bot (@typescript-bot) perf test

typescript-automation · 2026-11-05T18:55:10Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`perf test`	✅ Started	👀 Results

typescript-automation · 2026-11-05T19:56:09Z

Andrew Branch (@andrewbranch)
The results of the perf run you requested are in!

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_88,466	_88,466	_~	_~	_~	_{p=1.000 n=20}
_Types	_79,607	_79,607	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{106,381k (± 0.03%)}	_{106,422k (± 0.03%)}	_~	_106,322k	_106,553k	_{p=0.090 n=20}
_{Memory Allocs}	_{1,262,003 (± 0.01%)}	_{1,262,018 (± 0.01%)}	_~	_1,261,672	_1,262,547	_{p=0.952 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.023s (± 2.22%)}	_{0.023s (± 2.12%)}	_~	_0.021s	_0.025s	_{p=0.581 n=20}
_{Bind Time}	_{0.008s (± 4.45%)}	_{0.008s (± 5.21%)}	_~	_0.007s	_0.011s	_{p=0.464 n=20}
_{Check Time}	_{0.210s (± 2.35%)}	_{0.208s (± 0.92%)}	_~	_0.201s	_0.218s	_{p=0.825 n=20}
_{Emit Time}	_{0.137s (± 2.13%)}	_{0.135s (± 1.90%)}	_~	_0.129s	_0.155s	_{p=0.101 n=20}
_{Total Time}	_{0.381s (± 1.97%)}	_{0.378s (± 1.20%)}	_~	_0.368s	_0.412s	_{p=0.515 n=20}
_{angular-1 - native}
_Errors	₆₃	₆₃	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_756,637	_756,637	_~	_~	_~	_{p=1.000 n=20}
_Types	_549,451	_549,451	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{644,077k (± 0.01%)}	_{643,875k (± 0.02%)}	_{-202k (- 0.03%)}	_643,544k	_644,412k	_{p=0.013 n=20}
_{Memory Allocs}	_{9,539,758 (± 0.06%)}	_{9,496,053 (± 0.07%)}	_{-43,705 (- 0.46%)}	_9,487,433	_9,538,718	_{p=0.000 n=20}
_{Config Time}	_{0.008s (± 1.30%)}	_{0.006s (± 3.66%)}	_{🟩-0.002s (-20.50%)}	_0.006s	_0.007s	_{p=0.000 n=20}
_{Parse Time}	_{0.119s (± 4.66%)}	_{0.119s (± 5.05%)}	_~	_0.106s	_0.162s	_{p=0.963 n=20}
_{Bind Time}	_{0.041s (± 9.98%)}	_{0.042s (±10.64%)}	_~	_0.035s	_0.064s	_{p=0.686 n=20}
_{Check Time}	_{0.616s (± 1.21%)}	_{0.618s (± 1.18%)}	_~	_0.594s	_0.653s	_{p=0.867 n=20}
_{Emit Time}	_{0.393s (± 0.85%)}	_{0.390s (± 0.69%)}	_{-0.004s (- 0.90%)}	_0.385s	_0.410s	_{p=0.042 n=20}
_{Total Time}	_{1.192s (± 0.67%)}	_{1.187s (± 0.78%)}	_~	_1.161s	_1.239s	_{p=0.337 n=20}
_{arktype - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_686,116	_686,116	_~	_~	_~	_{p=1.000 n=20}
_Types	_939,797	_939,797	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{476,003k (± 0.01%)}	_{475,972k (± 0.01%)}	_~	_475,804k	_476,204k	_{p=0.365 n=20}
_{Memory Allocs}	_{12,058,818 (± 0.02%)}	_{12,051,242 (± 0.02%)}	_{-7,576 (- 0.06%)}	_12,046,819	_12,062,076	_{p=0.000 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.040s (± 4.39%)}	_{0.041s (± 3.81%)}	_~	_0.035s	_0.050s	_{p=0.430 n=20}
_{Bind Time}	_{0.014s (±10.14%)}	_{0.013s (± 9.05%)}	_~	_0.011s	_0.018s	_{p=0.271 n=20}
_{Check Time}	_{0.839s (± 1.31%)}	_{0.839s (± 1.17%)}	_~	_0.817s	_0.889s	_{p=0.888 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.921s (± 1.20%)}	_{0.920s (± 1.05%)}	_~	_0.899s	_0.971s	_{p=0.815 n=20}
_{class-transformer - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_45,376	_45,376	_~	_~	_~	_{p=1.000 n=20}
_Types	_7,573	_7,573	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{27,757k (± 0.03%)}	_{27,741k (± 0.03%)}	_{-16k (- 0.06%)}	_27,717k	_27,776k	_{p=0.002 n=20}
_{Memory Allocs}	_{248,339 (± 0.05%)}	_{247,678 (± 0.05%)}	_{-660 (- 0.27%)}	_247,292	_248,222	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.001s	_{🔻+0.001s (+ ∞%)}	_~	_~	_{p=0.000 n=20}
_{Parse Time}	_{0.011s (± 4.01%)}	_{0.011s (± 3.26%)}	_~	_0.009s	_0.012s	_{p=0.178 n=20}
_{Bind Time}	_{0.003s (±13.04%)}	_{0.003s (± 9.93%)}	_~	_0.002s	_0.005s	_{p=1.000 n=20}
_{Check Time}	_{0.008s (± 6.02%)}	_{0.008s (± 6.99%)}	_~	_0.006s	_0.010s	_{p=0.320 n=20}
_{Emit Time}	_{0.008s (± 4.96%)}	_{0.007s (± 5.92%)}	_~	_0.006s	_0.009s	_{p=0.285 n=20}
_{Total Time}	_{0.030s (± 2.46%)}	_{0.031s (± 1.44%)}	_~	_0.028s	_0.032s	_{p=0.301 n=20}
_{effect - native}
_Errors	₁₂	₁₂	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,235,134	_1,235,134	_~	_~	_~	_{p=1.000 n=20}
_Types	_893,436	_893,436	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{941,791k (± 0.03%)}	_{941,182k (± 0.02%)}	_{-609k (- 0.06%)}	_940,599k	_942,017k	_{p=0.001 n=20}
_{Memory Allocs}	_{12,625,088 (± 0.03%)}	_{12,589,950 (± 0.03%)}	_{-35,138 (- 0.28%)}	_12,577,021	_12,610,070	_{p=0.000 n=20}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.153s (± 1.33%)}	_{0.153s (± 1.73%)}	_~	_0.143s	_0.168s	_{p=0.541 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.925s (± 1.13%)}	_{0.934s (± 1.18%)}	_~	_0.883s	_0.995s	_{p=0.199 n=20}
_{Emit Time}	_{0.515s (± 1.80%)}	_{0.515s (± 1.25%)}	_~	_0.483s	_0.550s	_{p=0.551 n=20}
_{Total Time}	_{1.694s (± 0.71%)}	_{1.706s (± 0.61%)}	_~	_1.672s	_1.751s	_{p=0.199 n=20}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_3,782,394	_3,782,394	_~	_~	_~	_{p=1.000 n=20}
_Types	_1,355,778	_1,355,778	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{1,680,492k (± 0.08%)}	_{1,678,300k (± 0.07%)}	_{-2,192k (- 0.13%)}	_1,674,184k	_1,683,042k	_{p=0.006 n=20}
_{Memory Allocs}	_{25,756,831 (± 0.19%)}	_{25,534,928 (± 0.09%)}	_{-221,903 (- 0.86%)}	_25,488,784	_25,714,183	_{p=0.000 n=20}
_{Config Time}	_{0.008s (± 1.77%)}	_{0.006s (± 3.32%)}	_{🟩-0.002s (-22.84%)}	_0.006s	_0.007s	_{p=0.000 n=20}
_{Parse Time}	_{0.293s (± 5.48%)}	_{0.267s (± 2.02%)}	_{🟩-0.026s (- 9.02%)}	_0.241s	_0.290s	_{p=0.000 n=20}
_{Bind Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{2.881s (± 0.76%)}	_{2.894s (± 0.74%)}	_~	_2.783s	_2.964s	_{p=0.304 n=20}
_{Emit Time}	_{0.246s (± 1.42%)}	_{0.245s (± 1.25%)}	_~	_0.234s	_0.266s	_{p=0.909 n=20}
_{Total Time}	_{3.917s (± 0.79%)}	_{3.889s (± 0.58%)}	_~	_3.753s	_3.971s	_{p=0.314 n=20}
_{sentry - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_4,793,266	_4,793,266	_~	_~	_~	_{p=1.000 n=20}
_Types	_2,607,066	_2,607,066	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{2,798,816k (± 0.03%)}	_{2,797,850k (± 0.04%)}	_~	_2,795,010k	_2,803,875k	_{p=0.127 n=20}
_{Memory Allocs}	_{74,985,112 (± 0.21%)}	_{74,627,059 (± 0.08%)}	_{-358,053 (- 0.48%)}	_74,347,647	_74,917,795	_{p=0.000 n=20}
_{Config Time}	_{0.025s (± 0.58%)}	_{0.018s (± 1.36%)}	_{🟩-0.007s (-29.52%)}	_0.017s	_0.018s	_{p=0.000 n=20}
_{Parse Time}	_{0.468s (± 4.72%)}	_{0.457s (± 2.47%)}	_~	_0.418s	_0.505s	_{p=0.635 n=20}
_{Bind Time}	_{0.146s (± 9.22%)}	_{0.146s (± 9.43%)}	_~	_0.124s	_0.220s	_{p=0.493 n=20}
_{Check Time}	_{6.522s (± 0.39%)}	_{6.509s (± 0.52%)}	_~	_6.357s	_6.683s	_{p=0.402 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{7.212s (± 0.43%)}	_{7.178s (± 0.41%)}	_~	_7.063s	_7.330s	_{p=0.107 n=20}
_{social-app - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,883,060	_1,883,060	_~	_~	_~	_{p=1.000 n=20}
_Types	_1,158,093	_1,158,093	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{952,750k (± 0.02%)}	_{952,135k (± 0.02%)}	_{-616k (- 0.06%)}	_951,381k	_952,876k	_{p=0.000 n=20}
_{Memory Allocs}	_{13,496,203 (± 0.23%)}	_{13,399,267 (± 0.10%)}	_{-96,936 (- 0.72%)}	_13,363,088	_13,472,027	_{p=0.000 n=20}
_{Config Time}	_{0.007s (± 3.20%)}	_{0.006s (± 6.00%)}	_{🟩-0.002s (-23.49%)}	_0.005s	_0.008s	_{p=0.000 n=20}
_{Parse Time}	_{0.153s (± 2.39%)}	_{0.154s (± 4.87%)}	_~	_0.134s	_0.201s	_{p=0.401 n=20}
_{Bind Time}	_{0.042s (±10.45%)}	_{0.046s (±11.29%)}	_~	_0.035s	_0.070s	_{p=0.205 n=20}
_{Check Time}	_{1.399s (± 0.83%)}	_{1.391s (± 0.87%)}	_~	_1.340s	_1.441s	_{p=0.358 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.619s (± 0.71%)}	_{1.617s (± 0.87%)}	_~	_1.567s	_1.700s	_{p=0.616 n=20}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,184,972	_1,184,972	_~	_~	_~	_{p=1.000 n=20}
_Types	_438,823	_438,823	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{1,158,202k (± 0.32%)}	_{1,157,364k (± 0.30%)}	_~	_1,146,542k	_1,177,655k	_{p=0.758 n=20}
_{Memory Allocs}	_{47,578,700 (± 0.09%)}	_{47,419,923 (± 0.11%)}	_{-158,777 (- 0.33%)}	_47,186,295	_47,545,181	_{p=0.000 n=20}
_{Config Time}	_{0.002s (±52.68%)}	_{0.002s (±14.23%)}	_~	_0.001s	_0.004s	_{p=0.188 n=20}
_{Parse Time}	_{0.146s (± 8.12%)}	_{0.141s (± 4.69%)}	_~	_0.130s	_0.199s	_{p=0.109 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.801s (± 0.89%)}	_{0.803s (± 0.90%)}	_~	_0.778s	_0.831s	_{p=0.836 n=20}
_{Emit Time}	_{0.140s (± 1.60%)}	_{0.141s (± 1.81%)}	_~	_0.132s	_0.158s	_{p=0.835 n=20}
_{Total Time}	_{9.396s (± 1.00%)}	_{9.434s (± 1.38%)}	_~	_9.043s	_10.333s	_{p=0.779 n=20}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_263,481	_263,481	_~	_~	_~	_{p=1.000 n=20}
_Types	_196,103	_196,103	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{221,491k (± 0.01%)}	_{221,552k (± 0.02%)}	_{+61k (+ 0.03%)}	_221,355k	_221,695k	_{p=0.028 n=20}
_{Memory Allocs}	_{2,388,637 (± 0.02%)}	_{2,387,368 (± 0.01%)}	_{-1,269 (- 0.05%)}	_2,386,248	_2,388,441	_{p=0.000 n=20}
_{Config Time}	_{0.000s (±208.60%)}	_{0.000s (±95.71%)}	_~	_0.000s	_0.001s	_{p=0.342 n=20}
_{Parse Time}	_{0.049s (± 3.52%)}	_{0.050s (± 3.97%)}	_~	_0.044s	_0.060s	_{p=0.720 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.388s (± 2.29%)}	_{0.389s (± 2.35%)}	_~	_0.375s	_0.445s	_{p=0.899 n=20}
_{Emit Time}	_{0.053s (± 9.99%)}	_{0.049s (± 5.29%)}	_~	_0.043s	_0.061s	_{p=0.329 n=20}
_{Total Time}	_{0.519s (± 1.72%)}	_{0.517s (± 1.80%)}	_~	_0.494s	_0.576s	_{p=0.606 n=20}
_{t3code-server - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_4,349,937	_4,349,937	_~	_~	_~	_{p=1.000 n=20}
_Types	_3,042,465	_3,042,465	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{2,395,154k (± 0.02%)}	_{2,394,385k (± 0.03%)}	_{-769k (- 0.03%)}	_2,392,706k	_2,398,334k	_{p=0.011 n=20}
_{Memory Allocs}	_{37,128,398 (± 0.08%)}	_{36,999,988 (± 0.03%)}	_{-128,411 (- 0.35%)}	_36,957,236	_37,050,044	_{p=0.000 n=20}
_{Config Time}	_{0.003s (± 3.54%)}	_{0.002s (± 9.53%)}	_{🟩-0.001s (-22.03%)}	_0.002s	_0.003s	_{p=0.000 n=20}
_{Parse Time}	_{0.247s (± 2.13%)}	_{0.244s (± 3.46%)}	_~	_0.222s	_0.292s	_{p=0.159 n=20}
_{Bind Time}	_{0.086s (±10.00%)}	_{0.093s (±11.55%)}	_~	_0.075s	_0.143s	_{p=0.139 n=20}
_{Check Time}	_{5.869s (± 0.56%)}	_{5.861s (± 0.69%)}	_~	_5.706s	_6.107s	_{p=0.525 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{6.217s (± 0.57%)}	_{6.214s (± 0.64%)}	_~	_6.066s	_6.432s	_{p=0.606 n=20}
_{tanstack-router - native}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_570,149	_570,149	_~	_~	_~	_{p=1.000 n=20}
_Types	_396,551	_396,551	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{315,315k (± 0.02%)}	_{315,255k (± 0.02%)}	_~	_315,010k	_315,540k	_{p=0.144 n=20}
_{Memory Allocs}	_{4,333,086 (± 0.16%)}	_{4,315,574 (± 0.06%)}	_{-17,512 (- 0.40%)}	_4,308,847	_4,329,034	_{p=0.000 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.044s (± 2.94%)}	_{0.045s (± 2.99%)}	_~	_0.040s	_0.049s	_{p=0.110 n=20}
_{Bind Time}	_{0.016s (±13.77%)}	_{0.014s (± 9.73%)}	_~	_0.012s	_0.023s	_{p=0.500 n=20}
_{Check Time}	_{0.526s (± 0.71%)}	_{0.524s (± 0.67%)}	_~	_0.512s	_0.541s	_{p=0.343 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.604s (± 0.84%)}	_{0.605s (± 0.89%)}	_~	_0.586s	_0.628s	_{p=0.995 n=20}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_231,607	_231,607	_~	_~	_~	_{p=1.000 n=20}
_Types	_181,163	_181,163	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{190,851k (± 0.01%)}	_{190,837k (± 0.02%)}	_~	_190,682k	_190,929k	_{p=0.673 n=20}
_{Memory Allocs}	_{1,310,078 (± 0.02%)}	_{1,310,194 (± 0.02%)}	_~	_1,309,397	_1,311,237	_{p=0.478 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.040s (± 2.75%)}	_{0.041s (± 2.84%)}	_~	_0.037s	_0.045s	_{p=0.106 n=20}
_{Bind Time}	_{0.021s (± 4.78%)}	_{0.021s (± 4.56%)}	_~	_0.018s	_0.026s	_{p=0.843 n=20}
_{Check Time}	_{0.302s (± 0.93%)}	_{0.302s (± 1.46%)}	_~	_0.293s	_0.330s	_{p=0.349 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.370s (± 0.67%)}	_{0.371s (± 1.19%)}	_~	_0.363s	_0.398s	_{p=0.732 n=20}
_{vscode - native}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_7,887,624	_7,887,624	_~	_~	_~	_{p=1.000 n=20}
_Types	_4,623,231	_4,623,231	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{5,298,619k (± 0.02%)}	_{5,296,126k (± 0.02%)}	_{-2,493k (- 0.05%)}	_5,293,211k	_5,303,295k	_{p=0.001 n=20}
_{Memory Allocs}	_{59,426,882 (± 0.02%)}	_{58,390,075 (± 0.01%)}	_{-1,036,807 (- 1.74%)}	_58,373,065	_58,436,926	_{p=0.000 n=20}
_{Config Time}	_{0.034s (± 0.88%)}	_{0.025s (±20.34%)}	_{🟩-0.009s (-25.19%)}	_0.022s	_0.072s	_{p=0.000 n=20}
_{Parse Time}	_{0.921s (± 1.05%)}	_{0.907s (± 4.34%)}	_{-0.014s (- 1.56%)}	_0.828s	_1.230s	_{p=0.008 n=20}
_{Bind Time}	_{0.296s (± 0.70%)}	_{0.320s (± 6.33%)}	_~	_0.289s	_0.437s	_{p=0.329 n=20}
_{Check Time}	_{7.084s (± 0.72%)}	_{7.079s (± 1.10%)}	_~	_6.838s	_7.552s	_{p=0.542 n=20}
_{Emit Time}	_{2.042s (± 4.03%)}	_{2.194s (± 8.21%)}	_~	_1.941s	_2.943s	_{p=0.337 n=20}
_{Total Time}	_{10.435s (± 0.67%)}	_{10.589s (± 1.53%)}	_~	_10.236s	_11.263s	_{p=0.551 n=20}
_{webpack - native}
_Errors	₆₁₅	₆₁₅	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_883,161	_883,161	_~	_~	_~	_{p=1.000 n=20}
_Types	_621,386	_621,386	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{645,731k (± 0.02%)}	_{645,556k (± 0.02%)}	_{-175k (- 0.03%)}	_645,206k	_646,043k	_{p=0.034 n=20}
_{Memory Allocs}	_{6,049,186 (± 0.05%)}	_{6,019,993 (± 0.11%)}	_{-29,192 (- 0.48%)}	_6,004,628	_6,045,232	_{p=0.000 n=20}
_{Config Time}	_0.004s	_{0.003s (± 6.90%)}	_{🟩-0.001s (-15.00%)}	_0.003s	_0.004s	_{p=0.000 n=20}
_{Parse Time}	_{0.133s (± 2.09%)}	_{0.131s (± 2.19%)}	_~	_0.122s	_0.147s	_{p=0.239 n=20}
_{Bind Time}	_{0.044s (± 8.86%)}	_{0.045s (± 9.40%)}	_~	_0.037s	_0.070s	_{p=0.752 n=20}
_{Check Time}	_{1.084s (± 0.74%)}	_{1.084s (± 0.82%)}	_~	_1.044s	_1.117s	_{p=0.794 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.290s (± 0.71%)}	_{1.289s (± 0.74%)}	_~	_1.255s	_1.327s	_{p=0.597 n=20}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_644,330	_644,330	_~	_~	_~	_{p=1.000 n=20}
_Types	_392,175	_392,175	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{346,914k (± 0.02%)}	_{346,959k (± 0.03%)}	_~	_346,587k	_347,543k	_{p=0.678 n=20}
_{Memory Allocs}	_{3,998,883 (± 0.07%)}	_{4,009,701 (± 0.21%)}	_{+10,818 (+ 0.27%)}	_3,985,379	_4,046,737	_{p=0.044 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.060s (± 2.24%)}	_{0.064s (± 3.58%)}	_{🔻+0.004s (+ 6.76%)}	_0.055s	_0.077s	_{p=0.003 n=20}
_{Bind Time}	_{0.022s (±10.31%)}	_{0.018s (± 5.16%)}	_{🟩-0.004s (-18.78%)}	_0.016s	_0.024s	_{p=0.001 n=20}
_{Check Time}	_{0.439s (± 1.46%)}	_{0.433s (± 1.89%)}	_{-0.006s (- 1.33%)}	_0.414s	_0.498s	_{p=0.023 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.527s (± 1.15%)}	_{0.522s (± 1.82%)}	_{-0.006s (- 1.05%)}	_0.500s	_0.599s	_{p=0.027 n=20}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
arktype - native
class-transformer - native
effect - native
mui-docs - native
sentry - native
social-app - native
strada-build-src - native
strada-compiler - native
t3code-server - native
tanstack-router - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₂₀
_Baseline	_baseline	₂₀

lsp

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{CompilerLSP - native}
_{Req 1 - updateOpen}	_{5ms (± 8.42%)}	_{5ms (± 8.11%)}	_~	_4ms	_8ms	_{p=0.883 n=20}
_{Req 2 - geterr}	_{137ms (± 1.11%)}	_{136ms (± 2.53%)}	_{-1ms (- 0.47%)}	_131ms	_166ms	_{p=0.047 n=20}
_{Req 3 - references}	_{29ms (± 6.30%)}	_{29ms (± 3.00%)}	_~	_26ms	_34ms	_{p=0.705 n=20}
_{Req 4 - navto}	_{14ms (± 2.64%)}	_{15ms (± 8.66%)}	_~	_13ms	_24ms	_{p=0.558 n=20}
_{Req 5 - completionInfo count}	_1,525	_1,525	_~	_~	_~	_{p=1.000 n=20}
_{Req 5 - completionInfo}	_{9ms (± 8.76%)}	_{8ms (± 5.52%)}	_~	_8ms	_12ms	_{p=0.964 n=20}
_{Compiler-UnionsLSP - native}
_{Req 1 - updateOpen}	_{5ms (± 7.48%)}	_{5ms (± 9.41%)}	_~	_5ms	_8ms	_{p=0.477 n=20}
_{Req 2 - geterr}	_{268ms (± 1.42%)}	_{268ms (± 1.23%)}	_~	_255ms	_277ms	_{p=0.984 n=20}
_{Req 3 - references}	_{28ms (± 2.47%)}	_{28ms (± 2.15%)}	_~	_27ms	_32ms	_{p=0.130 n=20}
_{Req 4 - navto}	_{16ms (± 3.85%)}	_{16ms (± 4.63%)}	_~	_15ms	_20ms	_{p=0.720 n=20}
_{Req 5 - completionInfo count}	_1,363	_1,363	_~	_~	_~	_{p=1.000 n=20}
_{Req 5 - completionInfo}	_{10ms (±10.48%)}	_{11ms (±10.97%)}	_~	_8ms	_15ms	_{p=0.125 n=20}
_{xstate-main-1-LSP - native}
_{⚠️ Failed}	_failed	_failed

System info unknown

Hosts

native

Scenarios

CompilerLSP - native
Compiler-UnionsLSP - native
xstate-main-1-LSP - native

_Benchmark	_Name	_Iterations
_Current	_pr	₂₀
_Baseline	_baseline	₂₀

startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr
_{lsp-startup - native}
_{⚠️ Failed}	_failed	_failed
_{tsgo-startup - native}
_{⚠️ Failed}	_failed	_failed

System info unknown

Hosts

native

Scenarios

lsp-startup - native
tsgo-startup - native

_Benchmark	_Name	_Iterations
_Current	_pr	₂₀
_Baseline	_baseline	₂₀

Developer Information:

Download Benchmarks

Copilot

🟡 Changes recommended

The prefetch implementation limits active reads but not goroutine creation, allowing wide directories to spawn thousands of waiting goroutines and incur excessive memory and scheduling overhead.

1 open issue

Bound goroutine creation as well as active directory reads · New

_{Review effort: Balanced}

Andrew Branch (andrewbranch) · 2026-11-05T22:23:47Z

+}
+
+func (p *directoryPrefetcher) queue(item prefetchItem) {
+	p.wg.Queue(func() { p.run(item) })


Tested this, and it was 11% slower. This is the pattern parsing and binding use too.

typescript-automation Bot assigned Andrew Branch (andrewbranch) Oct 19, 2026

typescript-automation Bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Oct 19, 2026

Andrew Branch (andrewbranch) requested a balanced review from Copilot October 19, 2026 20:15

Copilot started reviewing on behalf of Andrew Branch (andrewbranch) October 19, 2026 20:15

View session

This comment was marked as resolved.

Sign in to view

Andrew Branch (andrewbranch) force-pushed the lsp-perf branch from d248609 to 8384f49 Compare October 19, 2026 20:56

Andrew Branch (andrewbranch) requested a balanced review from Copilot October 19, 2026 20:56

Copilot started reviewing on behalf of Andrew Branch (andrewbranch) October 19, 2026 20:57

View session

This comment was marked as resolved.

Sign in to view

Andrew Branch (andrewbranch) force-pushed the lsp-perf branch from 8384f49 to 06d2d96 Compare October 19, 2026 21:09

Andrew Branch (andrewbranch) requested a balanced review from Copilot October 19, 2026 21:09

Copilot started reviewing on behalf of Andrew Branch (andrewbranch) October 19, 2026 21:10

View session

Copilot AI reviewed Oct 19, 2026

View reviewed changes

Jake Bailey (jakebailey) added the Domain: Performance Performance related label Oct 27, 2026

Andrew Branch (andrewbranch) and others added 2 commits November 5, 2026 09:31

Andrew Branch (andrewbranch) force-pushed the lsp-perf branch from 06d2d96 to 263b546 Compare November 5, 2026 17:57

Andrew Branch (andrewbranch) and others added 6 commits November 5, 2026 10:48

Andrew Branch (andrewbranch) and others added 3 commits November 5, 2026 10:48

Andrew Branch (andrewbranch) force-pushed the lsp-perf branch from 263b546 to 92eacf3 Compare November 5, 2026 18:53

Andrew Branch (andrewbranch) requested a balanced review from Copilot November 5, 2026 21:28

Copilot started reviewing on behalf of Andrew Branch (andrewbranch) November 5, 2026 21:28

View session

Copilot AI reviewed Nov 5, 2026

View reviewed changes

Andrew Branch (andrewbranch) marked this pull request as ready for review November 5, 2026 22:24

Andrew Branch (andrewbranch) requested a review from Jake Bailey (jakebailey) November 5, 2026 22:24

Jake Bailey (jakebailey) approved these changes Nov 5, 2026

View reviewed changes

Andrew Branch (andrewbranch) added this pull request to the merge queue Nov 5, 2026

Merged via the queue into microsoft:main with commit 7502ae1 Nov 5, 2026
34 checks passed

Andrew Branch (andrewbranch) deleted the lsp-perf branch November 5, 2026 23:19

Conversation

Andrew Branch (andrewbranch) commented Oct 19, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Baseline (vscode)

Cumulative result (merge-base 3789ddb vs HEAD, vscode, interleaved runs, n=6)

Experiments

1. dirty.SyncMap.LoadClean fast path in snapshotFSBuilder — COMMITTED (0a35842; benchmarks in dd354e654af)

2. parseTask hot/cold split (compiler/filesparser.go) — COMMITTED (cea07f4)

3. Concurrent directory prefetch in vfsmatch — COMMITTED (39911ff)

4. sourceFS seen-file tracking + overlayFS no-clone — COMMITTED (039e5dd)

5. packagejson.InfoCache cheap Clone — COMMITTED (14e9882; RWMutex variant squashed away)

6. autoimport Export 248 → 192 B — COMMITTED (b975755)

7. tsoptions extension-priority sibling keys — COMMITTED (c09c9b0)

8. Module resolution: resolve candidate once — COMMITTED (de88374)

9. tspath leading ./ / ../ fast path — COMMITTED (9496c1e)

10. parseTask references resolution PackageId — COMMITTED (02e334f)

11. Co-allocated referenced-file include reasons — COMMITTED (570e356)

Uh oh!

Andrew Branch (andrewbranch) commented Oct 19, 2026

Uh oh!

typescript-automation Bot commented Oct 19, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-automation Bot commented Oct 19, 2026

tsc

lsp

startup

Uh oh!

This comment was marked as resolved.

Uh oh!

This comment was marked as resolved.

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🔵 Needs a closer look

Uh oh!

Andrew Branch (andrewbranch) commented Oct 19, 2026

Uh oh!

typescript-automation Bot commented Oct 19, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-automation Bot commented Oct 19, 2026

tsc

lsp

startup

Uh oh!

Andrew Branch (andrewbranch) commented Nov 5, 2026

Uh oh!

typescript-automation Bot commented Nov 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-automation Bot commented Nov 5, 2026

tsc

lsp

startup

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟡 Changes recommended

Uh oh!

Andrew Branch (andrewbranch) Nov 5, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Andrew Branch (andrewbranch) commented Oct 19, 2026 •

edited

Loading

Cumulative result (merge-base `3789ddb` vs HEAD, vscode, interleaved runs, n=6)

1. `dirty.SyncMap.LoadClean` fast path in snapshotFSBuilder — COMMITTED (`0a35842`; benchmarks in dd354e654af)

2. parseTask hot/cold split (compiler/filesparser.go) — COMMITTED (`cea07f4`)

3. Concurrent directory prefetch in vfsmatch — COMMITTED (`39911ff`)

4. sourceFS seen-file tracking + overlayFS no-clone — COMMITTED (`039e5dd`)

5. packagejson.InfoCache cheap Clone — COMMITTED (`14e9882`; RWMutex variant squashed away)

6. autoimport `Export` 248 → 192 B — COMMITTED (`b975755`)

7. tsoptions extension-priority sibling keys — COMMITTED (`c09c9b0`)

8. Module resolution: resolve candidate once — COMMITTED (`de88374`)

9. tspath leading `./` / `../` fast path — COMMITTED (`9496c1e`)

10. parseTask references resolution PackageId — COMMITTED (`02e334f`)

11. Co-allocated referenced-file include reasons — COMMITTED (`570e356`)

typescript-automation Bot commented Oct 19, 2026 •

edited

Loading

typescript-automation Bot commented Oct 19, 2026 •

edited

Loading

typescript-automation Bot commented Nov 5, 2026 •

edited

Loading