lib,src: improve histogram implementation by jasnell · Pull Request #65024 · nodejs/node · GitHub

Several improvements:

In histogram-inl, Add previous locked only this->mutex while
reading the other's fields unsafely.
In histogram.cc, PrepareCB now uses ContainerOf
In histogram.cc, BigInt value range is checked
In histogram.js, simplified impl and reduced duplication
In event_loop_delay.js, use a more consistent constructor
Add additional common histogram analysis operations

There is one potentially/technically breaking change. In Record, we were previously silently truncating when Bigint conversion was lossy. Now it throws. This is technically a bug fix. It's exceedingly unlikely that anyone is depending on the former behavior so I'd rather land this as a minor.

Signed-off-by: James M Snell jasnell@gmail.com
Assisted-by: Opencode/Opus

Several improvements: 1. In histogram-inl, Add previous locked only this->mutex while reading the other's fields unsafely. 2. In histogram.cc, PrepareCB now uses ContainerOf 3. In histogram.cc, BigInt value range is checked 4. In histogram.js, simplified impl and reduced duplication 5. In event_loop_delay.js, use a more consistent constructor Signed-off-by: James M Snell <jasnell@gmail.com> Assisted-by: Opencode/Opus

Signed-off-by: James M Snell <jasnell@gmail.com> Assisted-by: Opencode/Opus

Adds new analytical APIs to Histogram * histogram.ccdf(value) * histogram.cdf(value) * histogram.countAt(value) * histogram.ksTest(other) * histogram.kurtosis * histogram.linearBuckets(stepSize) * histogram.logBuckets(first, base) * histogram.percentilesAt(percentiles) * histogram.shewness On RecordableHistogram * histogram.recordCorrected(val, expectedInterval) * histogram.subtract(other) Signed-off-by: James M Snell <jasnell@gmail.com>

Codecov Report

❌ Patch coverage is 89.45578% with 62 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.32%. Comparing base (1576cb8) to head (4c5ff48).
⚠️ Report is 41 commits behind head on main.

Files with missing lines	Patch %	Lines
src/histogram.cc	86.03%	22 Missing and 21 partials ⚠️
src/histogram-inl.h	76.27%	8 Missing and 6 partials ⚠️
lib/internal/perf/event_loop_delay.js	72.72%	3 Missing ⚠️
lib/internal/histogram.js	98.97%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65024      +/-   ##
==========================================
+ Coverage   90.30%   90.32%   +0.01%     
==========================================
  Files         759      759              
  Lines      247634   248121     +487     
  Branches    46684    46798     +114     
==========================================
+ Hits       223630   224106     +476     
- Misses      15467    15475       +8     
- Partials     8537     8540       +3

Files with missing lines	Coverage Δ
src/histogram.h	68.42% <100.00%> (+18.42%)	⬆️
lib/internal/histogram.js	94.77% <98.97%> (+4.62%)	⬆️
lib/internal/perf/event_loop_delay.js	94.89% <72.72%> (-1.07%)	⬇️
src/histogram-inl.h	81.30% <76.27%> (-1.13%)	⬇️
src/histogram.cc	82.30% <86.03%> (+1.06%)	⬆️

... and 34 files with indirect coverage changes

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lgtm

CI: https://ci.nodejs.org/job/node-test-pull-request/75566/ 💛

Several improvements: 1. In histogram-inl, Add previous locked only this->mutex while reading the other's fields unsafely. 2. In histogram.cc, PrepareCB now uses ContainerOf 3. In histogram.cc, BigInt value range is checked 4. In histogram.js, simplified impl and reduced duplication 5. In event_loop_delay.js, use a more consistent constructor Adds new analytical APIs to Histogram * histogram.ccdf(value) * histogram.cdf(value) * histogram.countAt(value) * histogram.ksTest(other) * histogram.kurtosis * histogram.linearBuckets(stepSize) * histogram.logBuckets(first, base) * histogram.percentilesAt(percentiles) * histogram.shewness On RecordableHistogram * histogram.recordCorrected(val, expectedInterval) * histogram.subtract(other) Signed-off-by: James M Snell <jasnell@gmail.com> Assisted-by: Opencode/Opus PR-URL: #65024 Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Landed in bfa3e98

Several improvements: 1. In histogram-inl, Add previous locked only this->mutex while reading the other's fields unsafely. 2. In histogram.cc, PrepareCB now uses ContainerOf 3. In histogram.cc, BigInt value range is checked 4. In histogram.js, simplified impl and reduced duplication 5. In event_loop_delay.js, use a more consistent constructor Adds new analytical APIs to Histogram * histogram.ccdf(value) * histogram.cdf(value) * histogram.countAt(value) * histogram.ksTest(other) * histogram.kurtosis * histogram.linearBuckets(stepSize) * histogram.logBuckets(first, base) * histogram.percentilesAt(percentiles) * histogram.shewness On RecordableHistogram * histogram.recordCorrected(val, expectedInterval) * histogram.subtract(other) Signed-off-by: James M Snell <jasnell@gmail.com> Assisted-by: Opencode/Opus PR-URL: #65024 Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

The notable-change PRs with changes that should be highlighted in changelogs. label has been added by @jasnell.

Please suggest a text for the release notes if you'd like to include a more detailed summary, then proceed to update the PR description with the text or a link to the notable change suggested text comment. Otherwise, the commit will be placed in the Other Notable Changes section.

The notable-change PRs with changes that should be highlighted in changelogs. label has been added by @jasnell.

Please suggest a text for the release notes if you'd like to include a more detailed summary, then proceed to update the PR description with the text or a link to the notable change suggested text comment. Otherwise, the commit will be placed in the Other Notable Changes section.

Notes for the notable change:

This PR introduces a new set of statistical analysis algorithms for Histogram: ccdf(...), cdf(...), ksTest(...), kurtosis, skewness, linear buckets, log buckets, diffing, etc.

Several improvements: 1. In histogram-inl, Add previous locked only this->mutex while reading the other's fields unsafely. 2. In histogram.cc, PrepareCB now uses ContainerOf 3. In histogram.cc, BigInt value range is checked 4. In histogram.js, simplified impl and reduced duplication 5. In event_loop_delay.js, use a more consistent constructor Adds new analytical APIs to Histogram * histogram.ccdf(value) * histogram.cdf(value) * histogram.countAt(value) * histogram.ksTest(other) * histogram.kurtosis * histogram.linearBuckets(stepSize) * histogram.logBuckets(first, base) * histogram.percentilesAt(percentiles) * histogram.shewness On RecordableHistogram * histogram.recordCorrected(val, expectedInterval) * histogram.subtract(other) Signed-off-by: James M Snell <jasnell@gmail.com> Assisted-by: Opencode/Opus PR-URL: #65024 Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Notable changes: benchmark: * (SEMVER-MINOR) add --analyze mode to compare.js (James M Snell) #65416 crypto: * update root certificates to NSS 3.126 (Node.js GitHub Bot) #65495 * (SEMVER-MINOR) enable SIV and GCM-SIV modes in Cipher/Decipher APIs (Filip Skokan) #63411 diagnostics_channel: * mark TracingChannel as stable (Abdelrahman Awad) #64525 lib,src: * (SEMVER-MINOR) improve histogram implementation (James M Snell) #65024 net: * (SEMVER-MINOR) improve performance of net.BlockList (James M Snell) #64974 perf_hooks: * (SEMVER-MINOR) add statistical hypothesis testing to histogram (James M Snell) #65416 repl: * add basic syntax highlighting (Aviv Keller) #64591 sqlite: * (SEMVER-MINOR) add StatementSync.prototype.close() (Guilherme Araújo) #64232 * (SEMVER-MINOR) add StatementSync.prototype[Symbol.dispose]() (Guilherme Araújo) #64232 util: * (SEMVER-MINOR) add non-throwing MIMEType.parse (James M Snell) #64965 zlib: * (SEMVER-MINOR) add ZipEntry, ZipFile, and ZipBuffer (Philipp Dunkel) #64339 PR-URL: #65551

jasnell added 4 commits August 4, 2026 08:39

src: fix histogram mutex locking

63c43c1

Signed-off-by: James M Snell <jasnell@gmail.com> Assisted-by: Opencode/Opus

src: improvement histogram implementation

1568571

Signed-off-by: James M Snell <jasnell@gmail.com> Assisted-by: Opencode/Opus

jasnell added the semver-minor PRs that contain new features and should be released in the next minor version. label Aug 4, 2026

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. needs-ci PRs that need a full CI run. labels Aug 4, 2026

jasnell requested review from BridgeAR and mcollina August 5, 2026 14:55

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jasnell added author ready PRs that have at least one approval, no outstanding review comments, and a CI started. commit-queue-squash Add this label to instruct the Commit Queue to squash all the PR commits into the first one. labels Aug 6, 2026

jasnell closed this Aug 12, 2026

jasnell added the notable-change PRs with changes that should be highlighted in changelogs. label Aug 20, 2026

jasnell added notable-change PRs with changes that should be highlighted in changelogs. and removed notable-change PRs with changes that should be highlighted in changelogs. labels Aug 20, 2026

github-actions Bot mentioned this pull request Aug 25, 2026

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

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