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perf: reduce string allocation in sourcemap encoding#163

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Boshen merged 1 commit intomainfrom
09-23-perf_reduce_string_allocation_in_sourcemap_encoding
Sep 24, 2025
Merged

perf: reduce string allocation in sourcemap encoding#163
Boshen merged 1 commit intomainfrom
09-23-perf_reduce_string_allocation_in_sourcemap_encoding

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@Brooooooklyn Brooooooklyn commented Sep 23, 2025 •
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Only allocate once in fn to_json_string

@Brooooooklyn Brooooooklyn marked this pull request as draft September 23, 2025 15:42
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Brooooooklyn commented Sep 23, 2025

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codspeed-hq bot commented Sep 23, 2025 •
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CodSpeed Performance Report

Merging #163 will degrade performances by 2.25%

Comparing 09-23-perf_reduce_string_allocation_in_sourcemap_encoding (17d9e9b) with main (5f9c22d)

Summary

⚡ 2 improvements
❌ 2 regressions
✅ 1 untouched

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

Benchmark BASE HEAD Change
⚡ from_json_string 16.8 µs 16.6 µs +1.05%
❌ generate_lookup_table 1.3 µs 1.3 µs -2.25%
❌ to_json 5.5 µs 5.7 µs -2.2%
⚡ to_json_string 6.8 µs 5.4 µs +26.93%

@Brooooooklyn Brooooooklyn marked this pull request as ready for review September 23, 2025 15:43
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Pull Request Overview

This PR optimizes sourcemap JSON serialization by reducing string allocations in the encoding process. The refactoring replaces multiple Cow<str> allocations with direct string operations.

  • Refactors encode_to_string to use direct string writes via escape_into functions instead of Cow<str> wrappers
  • Simplifies PreAllocatedString to use a single String buffer instead of a vector of string segments
  • Improves serialize_sourcemap_mappings to write directly into the output buffer

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 3 comments.

File Description
src/encode.rs Comprehensive refactoring of string allocation patterns to reduce memory overhead in JSON encoding
CHANGELOG.md Fixes typo from "optimzed" to "optimized"

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@Brooooooklyn Brooooooklyn marked this pull request as draft September 23, 2025 16:19
@Brooooooklyn Brooooooklyn force-pushed the 09-23-perf_reduce_string_allocation_in_sourcemap_encoding branch from 05e8517 to 17d9e9b Compare September 24, 2025 02:16
@Brooooooklyn Brooooooklyn marked this pull request as ready for review September 24, 2025 02:19
@Boshen Boshen merged commit 29f716c into main Sep 24, 2025
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@Boshen Boshen deleted the 09-23-perf_reduce_string_allocation_in_sourcemap_encoding branch September 24, 2025 02:52
This was referenced Sep 24, 2025
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graphite-app bot pushed a commit to rolldown/rolldown that referenced this pull request Sep 24, 2025
@Boshen
chore(deps): bump oxc-resolver, oxc-sourcemap, oxc-browserslist to la…
f95e298 
…test (#6317)

* oxc-project/oxc-sourcemap#158
* oxc-project/oxc-sourcemap#163
* oxc-project/oxc-resolver#727 (fixes memory leak)
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@Brooooooklyn @Boshen