module: cache nearest parent package.json per directory by codebytere · Pull Request #65326 · nodejs/node · GitHub

Cold require() of a 1000-module CommonJS tree gets ~6 % faster (100 runs, ***) and module/module-require.js type='.js' +13.7 %, by looking up the nearest parent package.json once per directory instead of once per file.

module/module-require.js n=10000 type='.js'                                     ***    13.69 %  ±2.36%
module/module-require.js n=10000 type='.json' | 'dir' (don't use this path)              -2.1 %  (relink noise is ±1 %)
cold require() of a generated 1000-module tree, flat layout          (100 runs) ***     6.37 %  ±1.76%
  same, pnpm-style symlinked node_modules                                       ***     6.56 %  ±0.90%
  same, with NODE_COMPILE_CACHE warm                                            ***     5.10 %  ±1.43%

getNearestParentPackageJSON(checkPath) - called for every CommonJS module to find "type", and by findPackageJSON - memoized per file, so N modules in a directory meant N calls into the native package.json reader. The result only depends on the directory the traversal starts from, so the JS-side cache is now keyed by that directory, derived with the same rule the native side uses (trailing separator → that directory, else dirname). With the permission model enabled the per-path behavior is kept, because the native call performs a per-path read check. Same return values, same objects, same lifetime (both caches were already permanent). 1000 native calls → 236 for the tree above.

Tests: behavior is unchanged; test-module-*, test-require-*, test-esm-*, es-module and test-permission-* (which exercises the per-path branch) pass. Happy to add a call-count test if wanted.

Disclosure: the code, test, measurements and this description were written by Claude Code, directed and reviewed by @codebytere.

Review requested:

@nodejs/loaders

Codecov Report

❌ Patch coverage is 97.95918% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.13%. Comparing base (30bff4a) to head (feee201).
⚠️ Report is 43 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/modules/package_json_reader.js	97.95%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #65326   +/-   ##
=======================================
  Coverage   90.13%   90.13%           
=======================================
  Files         752      752           
  Lines      251568   251639   +71     
  Branches    47270    47285   +15     
=======================================
+ Hits       226759   226827   +68     
- Misses      16168    16174    +6     
+ Partials     8641     8638    -3

Files with missing lines	Coverage Δ
lib/internal/modules/package_json_reader.js	99.23% <97.95%> (-0.22%)	⬇️

... and 38 files with indirect coverage changes

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CI: https://ci.nodejs.org/job/node-test-pull-request/75894/

This seems good, but surely there should be some tests that assert the caching behavior, to avoid regressions?

getNearestParentPackageJSON() memoized its answer per file, so every module loaded still made one native call, and TraverseParent() builds several std::filesystem::path temporaries per directory level and serializes the whole package.json, which the JS side then usually discarded because it already had that package.json deserialized. The native traversal starts at the directory of the given path, so the answer only depends on that directory: key the memo by it (following NormalizePath()'s trailing-separator rule), so that all modules in a directory share one native call. When the permission model is enabled the traversal also depends on the read permissions in effect at call time, so that configuration keeps the per-file cache. Loading a 1000-module tree spread over ~240 directories goes from 1000 to 236 native calls. Signed-off-by: Shelley Vohr <shelley.vohr@gmail.com>

@ljharb done

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----------------------------------- PR info ------------------------------------
Title      module: cache nearest parent package.json per directory (#65326)
Author     Shelley Vohr <shelley.vohr@gmail.com> (@codebytere)
Branch     codebytere:perf/module-parent-package-json-dir-cache -> nodejs:main
Labels     module, commit-queue
Commits    1
 - module: cache nearest parent package.json per directory
Committers 1
 - Shelley Vohr <shelley.vohr@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/65326
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jordan Harband <ljharb@gmail.com>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/65326
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jordan Harband <ljharb@gmail.com>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Sun, 16 Aug 2026 15:51:12 GMT
   ✔  Approvals: 3
   ✔  - Yagiz Nizipli (@anonrig) (TSC): https://github.com/nodejs/node/pull/65326#pullrequestreview-4947040173
   ✔  - James M Snell (@jasnell) (TSC): https://github.com/nodejs/node/pull/65326#pullrequestreview-4948264808
   ✔  - Jordan Harband (@ljharb): https://github.com/nodejs/node/pull/65326#pullrequestreview-4953177652
   ✔  Last GitHub CI successful
   ℹ  Last Full PR CI on 2026-08-16T18:43:54Z: https://ci.nodejs.org/job/node-test-pull-request/75894/
   ⚠  Commits were pushed after the last Full PR CI run:
   ⚠  - module: cache nearest parent package.json per directory
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https://github.com/nodejs/node/actions/runs/32157693157

CI: https://ci.nodejs.org/job/node-test-pull-request/75973/

CI: https://ci.nodejs.org/job/node-test-pull-request/75982/

Landed in 9c641c5

getNearestParentPackageJSON() memoized its answer per file, so every module loaded still made one native call, and TraverseParent() builds several std::filesystem::path temporaries per directory level and serializes the whole package.json, which the JS side then usually discarded because it already had that package.json deserialized. The native traversal starts at the directory of the given path, so the answer only depends on that directory: key the memo by it (following NormalizePath()'s trailing-separator rule), so that all modules in a directory share one native call. When the permission model is enabled the traversal also depends on the read permissions in effect at call time, so that configuration keeps the per-file cache. Loading a 1000-module tree spread over ~240 directories goes from 1000 to 236 native calls. Signed-off-by: Shelley Vohr <shelley.vohr@gmail.com> PR-URL: #65326 Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Jordan Harband <ljharb@gmail.com>

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codebytere requested review from GeoffreyBooth, IlyasShabi and anonrig August 16, 2026 18:36

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codebytere force-pushed the perf/module-parent-package-json-dir-cache branch from cbba4de to feee201 Compare August 17, 2026 06:25

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2026-08-26, Version 26.8.0 (Current) #65551

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module: cache nearest parent package.json per directory by codebytere · Pull Request #65326 · nodejs/node · GitHub

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