Allocate node and symbol IDs in per-checker blocks by mds-ant · Pull Request #4741 · microsoft/typescript-go

mds-ant · 2026-07-25T15:21:04Z

Context

Node and symbol IDs are assigned on first touch from two global counters. With several checkers running at once, the IDs each checker sees are interleaved with everyone else's, so the paged link stores from #4329 (which allocate 256-slot pages keyed by ID) materialize pages that are mostly slots for entities the checker never touches. The first-touch assignment is also a contended atomic increment on shared symbols and nodes.

This PR

In this PR, we give each Checker an ast.IdAllocator that reserves contiguous, page-aligned blocks of IDs from the global counters and hands them out locally. The first checker to touch a node or symbol is usually the one that owns its file, so IDs cluster per checker and the pages of symbolNodeLinks and valueSymbolLinks become dense. Block size grows from 256 IDs up to 4096 IDs so that short-lived checkers waste at most a page while batch checkers still amortize reservations.

Performance

VS Code src (8,474 files, --noEmit):

Configuration	main wall	branch wall	delta
1 checker	19.290 s	19.298 s	within noise
4 checkers	6.191 s	5.986 s	−3.3%
8 checkers	4.319 s	4.101 s	−5.1%
16 checkers	3.514 s	3.070 s	−12.6%

Memory

Link store pages are no longer duplicated across checkers for entities only one checker touches:

4 checkers: 146,423 pages → 68,906 pages
16 checkers: 610,118 pages → 134,491 pages

Configuration	main peak RSS	branch peak RSS	delta
1 checker	4,346 MB	4,283 MB	within noise
4 checkers	5,206 MB	5,088 MB	−118 MB
8 checkers	6,122 MB	5,608 MB	−514 MB
16 checkers	7,210 MB	6,179 MB	−1,031 MB

This PR was assisted by Claude Code.

Node and symbol ids are assigned lazily on first touch from two global atomic counters. With multiple checkers running concurrently the ids each checker sees are interleaved with every other checker's, so the paged link stores (which index 256-entry pages by id) end up allocating pages that are mostly slots for entities the checker never touches, and the first-touch assignment itself is a contended atomic increment on symbols and nodes shared between checkers. Give each checker an `ast.IdAllocator` that reserves page-aligned blocks of ids from the global counters and hands them out locally. The first checker to touch a node or symbol is almost always the one that owns the file it belongs to, so ids now cluster per checker and the pages of `symbolNodeLinks` and `valueSymbolLinks` become dense. Callers outside the checker keep using the plain `GetNodeId`/`GetSymbolId`.

mds-ant · 2026-07-25T15:21:55Z

cc: @ahejlsberg @jakebailey

Copilot

Pull request overview

Adds per-checker, page-aligned ID allocation to improve paged link-store density and reduce atomic-counter contention.

Changes:

Introduces adaptive block-based node and symbol ID allocation.
Integrates allocators into checker paged link stores.
Adds allocator exclusivity coverage and updates related documentation.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
`internal/core/linkstore.go`	Exposes the link-store page size.
`internal/checker/links.go`	Uses checker-local ID allocation for paged stores.
`internal/checker/checker.go`	Initializes each checker’s allocator.
`internal/ast/utilities.go`	Moves global ID logic into `ids.go`.
`internal/ast/ids.go`	Implements global and block-based ID allocation.
`internal/ast/ids_test.go`	Tests page ownership across allocators.
`internal/api/session.go`	Updates symbol-ID documentation.

jakebailey · 2026-07-25T15:27:51Z

@typescript-bot perf test this

typescript-automation · 2026-07-25T15:27:56Z

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

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

typescript-automation · 2026-07-25T15:53:59Z

@jakebailey
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	₄	₄	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_{81,800 (± 0.02%)}	_{81,823 (± 0.04%)}	_~	_81,795	_81,860	_{p=0.470 n=6}
_Types	_98,817	_98,817	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{176,485k (± 0.29%)}	_{175,191k (± 0.37%)}	_{-1,294k (- 0.73%)}	_174,146k	_175,860k	_{p=0.008 n=6}
_{Memory Allocs}	_{2,695,442 (± 0.01%)}	_{2,695,129 (± 0.01%)}	_{-312 (- 0.01%)}	_2,694,929	_2,695,319	_{p=0.020 n=6}
_{Config Time}	_0.001s	_{0.001s (±109.43%)}	_~	_0.000s	_0.001s	_{p=0.071 n=6}
_{Parse Time}	_{0.065s (± 8.06%)}	_{0.062s (±11.44%)}	_~	_0.052s	_0.073s	_{p=0.573 n=6}
_{Bind Time}	_{0.019s (±17.80%)}	_{0.018s (±16.83%)}	_~	_0.013s	_0.022s	_{p=0.747 n=6}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=6}
_{Emit Time}	_{0.967s (± 1.43%)}	_{0.963s (± 1.35%)}	_~	_0.950s	_0.984s	_{p=0.689 n=6}
_{Total Time}	_{1.054s (± 1.49%)}	_{1.045s (± 1.88%)}	_~	_1.021s	_1.074s	_{p=0.470 n=6}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_{872,497 (± 0.16%)}	_{872,108 (± 0.11%)}	_~	_870,918	_872,998	_{p=0.689 n=6}
_Types	_{263,962 (± 0.00%)}	_{263,962 (± 0.00%)}	_~	_263,960	_263,965	_{p=0.867 n=6}
_{Memory Used}	_{828,862k (± 0.07%)}	_{811,232k (± 0.12%)}	_{-17,630k (- 2.13%)}	_810,209k	_812,759k	_{p=0.005 n=6}
_{Memory Allocs}	_{13,184,934 (± 0.11%)}	_{13,180,657 (± 0.24%)}	_~	_13,162,517	_13,244,448	_{p=0.066 n=6}
_{Config Time}	_{0.027s (±11.93%)}	_{0.025s (±13.74%)}	_~	_0.022s	_0.032s	_{p=0.469 n=6}
_{Parse Time}	_{0.272s (± 4.76%)}	_{0.265s (± 1.49%)}	_~	_0.261s	_0.272s	_{p=0.377 n=6}
_{Bind Time}	_{0.048s (±14.13%)}	_{0.047s (±15.65%)}	_~	_0.041s	_0.061s	_{p=0.629 n=6}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=6}
_{Emit Time}	_{2.109s (± 1.74%)}	_{2.056s (± 2.39%)}	_~	_1.996s	_2.137s	_{p=0.173 n=6}
_{Total Time}	_{2.469s (± 1.07%)}	_{2.407s (± 1.77%)}	_{-0.062s (- 2.50%)}	_2.363s	_2.476s	_{p=0.044 n=6}
_{mui-docs - native}
_Errors	_{11,277 (± 0.05%)}	_{11,280 (± 0.02%)}	_~	_11,277	_11,282	_{p=0.162 n=6}
_Symbols	_4,448,802	_4,448,802	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,659,690	_1,659,690	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{5,072,169k (± 0.03%)}	_{5,009,225k (± 0.02%)}	_{-62,945k (- 1.24%)}	_5,008,320k	_5,010,415k	_{p=0.005 n=6}
_{Memory Allocs}	_{51,237,083 (± 0.04%)}	_{51,235,351 (± 0.04%)}	_~	_51,205,836	_51,261,040	_{p=0.936 n=6}
_{Config Time}	_{0.029s (± 5.13%)}	_{0.028s (± 7.67%)}	_~	_0.025s	_0.030s	_{p=0.183 n=6}
_{Parse Time}	_{0.587s (± 1.84%)}	_{0.599s (± 2.29%)}	_~	_0.580s	_0.614s	_{p=0.149 n=6}
_{Bind Time}	_{0.002s (±22.11%)}	_{0.002s (±22.11%)}	_~	_0.002s	_0.003s	_{p=1.000 n=6}
_{Check Time}	_{19.683s (± 0.81%)}	_{19.642s (± 0.90%)}	_~	_19.493s	_19.980s	_{p=0.689 n=6}
_{Emit Time}	_{0.562s (±10.80%)}	_{0.548s (± 4.25%)}	_~	_0.536s	_0.595s	_{p=0.517 n=6}
_{Total Time}	_{21.753s (± 1.37%)}	_{21.686s (± 0.99%)}	_~	_21.475s	_22.061s	_{p=0.810 n=6}
_{self-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,394,220	_1,394,220	_~	_~	_~	_{p=1.000 n=6}
_Types	_442,210	_442,210	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{1,665,241k (± 0.39%)}	_{1,651,883k (± 0.43%)}	_{-13,358k (- 0.80%)}	_1,643,595k	_1,664,842k	_{p=0.045 n=6}
_{Memory Allocs}	_{97,314,623 (± 0.06%)}	_{97,280,667 (± 0.07%)}	_~	_97,197,972	_97,415,893	_{p=0.230 n=6}
_{Config Time}	_{0.024s (± 9.71%)}	_{0.024s (± 7.95%)}	_~	_0.021s	_0.026s	_{p=0.809 n=6}
_{Parse Time}	_{0.257s (± 4.92%)}	_{0.262s (± 2.74%)}	_~	_0.248s	_0.268s	_{p=0.873 n=6}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=6}
_{Check Time}	_{2.531s (± 1.28%)}	_{2.530s (± 0.55%)}	_~	_2.504s	_2.545s	_{p=0.575 n=6}
_{Emit Time}	_{0.352s (± 3.58%)}	_{0.349s (± 4.69%)}	_~	_0.319s	_0.360s	_{p=0.936 n=6}
_{Total Time}	_{32.772s (± 1.11%)}	_{32.663s (± 0.33%)}	_~	_32.580s	_32.850s	_{p=0.936 n=6}
_{self-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_337,681	_337,681	_~	_~	_~	_{p=1.000 n=6}
_Types	_199,559	_199,559	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{326,587k (± 0.04%)}	_{320,440k (± 0.03%)}	_{-6,147k (- 1.88%)}	_320,353k	_320,612k	_{p=0.005 n=6}
_{Memory Allocs}	_{4,685,021 (± 0.01%)}	_{4,682,413 (± 0.01%)}	_{-2,608 (- 0.06%)}	_4,681,761	_4,683,647	_{p=0.005 n=6}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=6}
_{Parse Time}	_{0.130s (± 5.24%)}	_{0.126s (± 4.07%)}	_~	_0.122s	_0.135s	_{p=0.199 n=6}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=6}
_{Check Time}	_{1.278s (± 1.07%)}	_{1.273s (± 0.44%)}	_~	_1.265s	_1.278s	_{p=0.627 n=6}
_{Emit Time}	_{0.120s (± 8.52%)}	_{0.116s (± 7.91%)}	_~	_0.107s	_0.125s	_{p=0.688 n=6}
_{Total Time}	_{1.584s (± 0.98%)}	_{1.568s (± 0.69%)}	_~	_1.550s	_1.581s	_{p=0.128 n=6}
_{ts-pre-modules - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_97,488	_97,488	_~	_~	_~	_{p=1.000 n=6}
_Types	₃₅₆	₃₅₆	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{133,738k (± 0.03%)}	_{133,740k (± 0.03%)}	_~	_133,706k	_133,791k	_{p=0.936 n=6}
_{Memory Allocs}	_{180,161 (± 0.21%)}	_{180,341 (± 0.18%)}	_~	_179,918	_180,755	_{p=0.298 n=6}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=6}
_{Parse Time}	_{0.114s (± 3.70%)}	_{0.117s (± 6.43%)}	_~	_0.108s	_0.126s	_{p=0.520 n=6}
_{Bind Time}	_{0.039s (±13.24%)}	_{0.036s (±12.53%)}	_~	_0.032s	_0.043s	_{p=0.572 n=6}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=6}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{0.156s (± 4.90%)}	_{0.157s (± 3.47%)}	_~	_0.148s	_0.162s	_{p=0.810 n=6}
_{vscode - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_7,359,695	_7,359,695	_~	_~	_~	_{p=1.000 n=6}
_Types	_2,577,579	_2,577,579	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{5,038,381k (± 0.03%)}	_{4,852,073k (± 0.03%)}	_{🟩-186,308k (- 3.70%)}	_4,850,419k	_4,854,412k	_{p=0.005 n=6}
_{Memory Allocs}	_{37,910,415 (± 0.12%)}	_{37,781,024 (± 0.06%)}	_{-129,390 (- 0.34%)}	_37,757,334	_37,813,764	_{p=0.005 n=6}
_{Config Time}	_{0.077s (± 8.07%)}	_{0.074s (± 7.59%)}	_~	_0.069s	_0.082s	_{p=0.470 n=6}
_{Parse Time}	_{0.963s (± 4.04%)}	_{0.956s (± 3.68%)}	_~	_0.895s	_0.978s	_{p=0.574 n=6}
_{Bind Time}	_{0.180s (±19.09%)}	_{0.174s (±16.26%)}	_~	_0.157s	_0.231s	_{p=1.000 n=6}
_{Check Time}	_{8.724s (± 0.90%)}	_{8.505s (± 0.53%)}	_{-0.219s (- 2.51%)}	_8.417s	_8.539s	_{p=0.005 n=6}
_{Emit Time}	_{2.540s (± 8.89%)}	_{2.528s (± 3.74%)}	_~	_2.412s	_2.653s	_{p=0.575 n=6}
_{Total Time}	_{12.506s (± 1.06%)}	_{12.258s (± 1.06%)}	_{-0.248s (- 1.98%)}	_12.067s	_12.417s	_{p=0.013 n=6}
_{webpack - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_193,333	_193,333	_~	_~	_~	_{p=1.000 n=6}
_Types	₃₄₀	₃₄₀	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{238,082k (± 0.09%)}	_{237,875k (± 0.15%)}	_~	_237,370k	_238,330k	_{p=0.471 n=6}
_{Memory Allocs}	_{985,188 (± 0.51%)}	_{980,776 (± 0.49%)}	_~	_973,223	_988,315	_{p=0.128 n=6}
_{Config Time}	_{0.008s (±32.29%)}	_{0.008s (±46.86%)}	_~	_0.006s	_0.016s	_{p=0.868 n=6}
_{Parse Time}	_{0.156s (± 5.92%)}	_{0.150s (± 7.42%)}	_~	_0.131s	_0.160s	_{p=0.470 n=6}
_{Bind Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=6}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=6}
_{Emit Time}	_{0.041s (±17.97%)}	_{0.051s (±39.88%)}	_~	_0.034s	_0.090s	_{p=0.378 n=6}
_{Total Time}	_{0.206s (± 4.48%)}	_{0.210s (± 9.11%)}	_~	_0.185s	_0.241s	_{p=0.810 n=6}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,064,618	_1,064,618	_~	_~	_~	_{p=1.000 n=6}
_Types	_392,776	_392,776	_~	_~	_~	_{p=1.000 n=6}
_{Memory Used}	_{648,770k (± 0.01%)}	_{630,926k (± 0.02%)}	_{-17,844k (- 2.75%)}	_630,759k	_631,165k	_{p=0.005 n=6}
_{Memory Allocs}	_{5,004,464 (± 0.12%)}	_{4,992,538 (± 0.04%)}	_{-11,926 (- 0.24%)}	_4,989,804	_4,994,740	_{p=0.008 n=6}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=6}
_{Parse Time}	_{0.125s (± 6.07%)}	_{0.131s (± 6.46%)}	_~	_0.121s	_0.142s	_{p=0.378 n=6}
_{Bind Time}	_{0.033s (±42.19%)}	_{0.032s (±21.82%)}	_~	_0.024s	_0.041s	_{p=0.746 n=6}
_{Check Time}	_{1.056s (± 0.66%)}	_{1.042s (± 1.08%)}	_~	_1.030s	_1.060s	_{p=0.077 n=6}
_{Emit Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{1.220s (± 1.24%)}	_{1.212s (± 0.87%)}	_~	_1.202s	_1.232s	_{p=0.423 n=6}

System info unknown

Hosts

native

Scenarios

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

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

lsp

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-UnionsLSP - native}
_{Req 1 - updateOpen}	_{10ms (± 4.01%)}	_10ms	_~	_~	_~	_{p=0.405 n=6}
_{Req 2 - geterr}	_{883ms (± 1.11%)}	_{881ms (± 1.41%)}	_~	_863ms	_894ms	_{p=0.810 n=6}
_{Req 3 - references}	_{41ms (± 9.71%)}	_{44ms (±20.10%)}	_~	_36ms	_58ms	_{p=0.936 n=6}
_{Req 4 - navto}	_{17ms (± 7.87%)}	_{18ms (±12.22%)}	_~	_16ms	_22ms	_{p=1.000 n=6}
_{Req 5 - completionInfo count}	_1,357	_1,357	_~	_~	_~	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{17ms (±28.79%)}	_{16ms (±13.48%)}	_~	_14ms	_19ms	_{p=1.000 n=6}
_{CompilerLSP - native}
_{Req 1 - updateOpen}	_11ms	_{11ms (± 3.76%)}	_~	_10ms	_11ms	_{p=0.405 n=6}
_{Req 2 - geterr}	_{435ms (± 2.48%)}	_{441ms (± 0.76%)}	_~	_438ms	_446ms	_{p=0.172 n=6}
_{Req 3 - references}	_{46ms (± 5.30%)}	_{46ms (± 9.18%)}	_~	_40ms	_51ms	_{p=1.000 n=6}
_{Req 4 - navto}	_{19ms (± 9.37%)}	_{18ms (± 3.13%)}	_~	_17ms	_18ms	_{p=0.138 n=6}
_{Req 5 - completionInfo count}	_1,519	_1,519	_~	_~	_~	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{19ms (±16.63%)}	_{19ms (±10.16%)}	_~	_17ms	_22ms	_{p=1.000 n=6}

System info unknown

Hosts

native

Scenarios

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

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{lsp-startup - native}
_{Execution time}	_{4.74ms (±516.54%)}	_{4.77ms (±516.55%)}	_{+0.03ms (+ 0.53%)}	_0.00ms	_481.83ms	_{p=0.001 n=600}
_{tsgo-startup - native}
_{Execution time}	_{5.87ms (±516.54%)}	_{5.92ms (±516.54%)}	_{+0.05ms (+ 0.87%)}	_0.00ms	_593.35ms	_{p=0.000 n=600}

System info unknown

Hosts

native

Scenarios

lsp-startup - native
tsgo-startup - native

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

Copilot AI review requested due to automatic review settings July 25, 2026 15:21

Copilot started reviewing on behalf of mds-ant July 25, 2026 15:21 View session

mds-ant changed the title ~~Allocate node and symbol ids in per-checker blocks~~ Allocate node and symbol IDs in per-checker blocks Jul 25, 2026

Copilot AI reviewed Jul 25, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Allocate node and symbol IDs in per-checker blocks - #4741

Allocate node and symbol IDs in per-checker blocks#4741
mds-ant wants to merge 1 commit into
microsoft:mainfrom
mds-ant:checker-id-blocks

mds-ant commented Jul 25, 2026

Uh oh!

mds-ant commented Jul 25, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

jakebailey commented Jul 25, 2026

Uh oh!

typescript-automation Bot commented Jul 25, 2026 •

edited

Loading

Uh oh!

typescript-automation Bot commented Jul 25, 2026

tsc

lsp

startup

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Uh oh!

Conversation

mds-ant commented Jul 25, 2026

Context

This PR

Performance

Memory

Uh oh!

mds-ant commented Jul 25, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

jakebailey commented Jul 25, 2026

Uh oh!

typescript-automation Bot commented Jul 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-automation Bot commented Jul 25, 2026

tsc

lsp

startup

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

typescript-automation Bot commented Jul 25, 2026 •

edited

Loading