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Presize checker type-list cache keys - #64794
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Jake Bailey (jakebailey) merged 1 commit intoOct 14, 2026
Merged
Jake Bailey (jakebailey) merged 1 commit into
Jake Bailey (jakebailey) merged 1 commit into
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Large type lists repeatedly grow temporary hash buffers even though
their encoded length is already known. These discarded allocations
account for a substantial part of checker allocation traffic.
Reserve enough capacity before writing each list, retaining the small
inline path and the exact existing hash byte stream. Allocation tests
cover the inline boundary and large lists, and a fresh-program benchmark
includes parsing and binding rather than relying only on warmed ASTs.
CPU wall timings are noisy on this machine; report bytes and allocation
counts instead.
goos: linux
goarch: amd64
pkg: github.com/microsoft/TypeScript/tsc/internal/checker
cpu: Intel(R) Core(TM) i9-10900K CPU @ 3.70GHz
│ key-before.txt │ key-reserve.txt │
│ B/op │ B/op vs base │
TypeListKey/8-20 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=6) ¹
TypeListKey/46-20 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=6) ¹
TypeListKey/47-20 576.0 ± 0% 208.0 ± 0% -63.89% (p=0.002 n=6)
TypeListKey/256-20 2.375Ki ± 0% 1.125Ki ± 0% -52.63% (p=0.002 n=6)
TypeListKey/4096-20 81.25Ki ± 0% 18.00Ki ± 0% -77.85% (p=0.002 n=6)
geomean ² -48.03% ²
¹ all samples are equal
² summaries must be >0 to compute geomean
│ key-before.txt │ key-reserve.txt │
│ allocs/op │ allocs/op vs base │
TypeListKey/8-20 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=6) ¹
TypeListKey/46-20 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=6) ¹
TypeListKey/47-20 2.000 ± 0% 1.000 ± 0% -50.00% (p=0.002 n=6)
TypeListKey/256-20 4.000 ± 0% 1.000 ± 0% -75.00% (p=0.002 n=6)
TypeListKey/4096-20 13.000 ± 0% 1.000 ± 0% -92.31% (p=0.002 n=6)
geomean ² -60.50% ²
¹ all samples are equal
² summaries must be >0 to compute geomean
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Jake Bailey (jakebailey)
added this pull request to stack #64805
October 13, 2026 20:16
Jake Bailey (jakebailey)
removed this pull request from stack #64805
October 13, 2026 20:49
Jake Bailey (jakebailey)
added this pull request to stack #64806
October 13, 2026 20:50
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🟢 Approval recommended
The reservation logic preserves encoding behavior and has focused correctness and allocation coverage.
0 open findings
What changed in this PR
Presizes checker type-list cache keys to reduce temporary buffer allocations without changing hashes.
Changes:
- Reserves encoded type-list capacity before writing.
- Adds hash-correctness and allocation-boundary tests.
- Adds focused key and fresh-program benchmarks.
| File | Description |
|---|---|
tsc/internal/checker/checker.go |
Presizes overflow buffers for type-list keys. |
tsc/internal/checker/types_test.go |
Tests correctness and allocation behavior. |
tsc/internal/checker/checker_test.go |
Benchmarks fresh-program checking. |
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Anders Hejlsberg (ahejlsberg)
approved these changes
Oct 13, 2026
Jake Bailey (jakebailey)
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October 14, 2026 01:07
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Large type lists repeatedly grow temporary hash buffers even though their encoded size is known up front.
Part of the memory optimization stack summarized in #64734.
Replaces #64777, which GitHub closed as merged when the stack was reordered.