ci: Benchmarks check fails on CI runner noise - #10704
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Organization UI Review profile: CHILL Plan: Essentials Run ID: 📒 Files selected for processing (3)
🚧 Files skipped from review as they are similar to previous changes (3)
Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review. 📝 WalkthroughWalkthroughThe PR adds configurable benchmark runs, a script to compare base and PR results and retest flagged regressions, and CI workflow changes that run the comparison and upload its reports. ChangesBenchmark comparison
Priority: ⬇️ Low Estimated code review effort: 3 (Moderate) | ~30 minutes Sequence Diagram(s)sequenceDiagram
participant CI as CI workflow
participant Compare as benchmark/compare.js
participant Base as base benchmark runner
participant PR as PR benchmark runner
CI->>Base: Run base benchmarks and write baseline results
CI->>PR: Run PR benchmarks and write PR results
CI->>Compare: Compare baseline and PR results
loop Retest flagged benchmarks
Compare->>Base: Run selected benchmarks for a retest round
Compare->>PR: Run selected benchmarks for a retest round
end
Compare-->>CI: Return comparison status and write report
Merge Risk: ⚪ Minimal · up to The benchmark check can retest flagged regressions and report confirmed slowdowns. No actionable merge-blocking risk was established. 🚥 Pre-merge checks | ✅ 7✅ Passed checks (7 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In @benchmark/compare.js:
- Around line 137-154: Update retest’s per-name completeness check so a result
is accepted only when both base and pr have at least rounds measurements for
that name. Treat missing results from failed benchmark runs or selected-name
filtering as incomplete, preserving the existing behavior for incomplete
retests.
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ℹ️ Review info
⚙️ Run configuration
Configuration used: Organization UI
Review profile: CHILL
Plan: Essentials
Run ID: c36d074b-55b6-4c37-88e7-b2a8d3e858ce
📒 Files selected for processing (5)
.github/workflows/ci-performance.ymlCONTRIBUTING.mdbenchmark/compare.jsbenchmark/performance.jsspec/BenchmarkCompare.spec.js
Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## alpha #10704 +/- ##
==========================================
+ Coverage 93.84% 93.88% +0.03%
==========================================
Files 192 193 +1
Lines 16937 17061 +124
Branches 257 257
==========================================
+ Hits 15894 16017 +123
- Misses 1021 1022 +1
Partials 22 22 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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🎉 This change has been released in version 9.10.2-alpha.5 |
2 participants
Pull Request
Issue
The required
Benchmarkscheck fails on CI runner noise. It compares one baseline measurement with one PR measurement taken minutes apart, so a slowdown of the runner during the PR measurement looks like a regression. All known false failures hit benchmarks with a median below 2 ms that measure for about a second or less, for exampleObject.save (create)at 0.52 → 0.66 ms (+26%) on a lock-file-only change in #10656. Each one costs a manual re-run of the job.Closes #10684, part of #10681.
Approach
When a benchmark is more than 25% slower, only that benchmark is measured again: 3 times for the base branch and 3 times for the PR, alternating between them (base, PR, PR, base, base, PR), each with a third of the iterations. The check only fails if the regression persists in the medians of these measurements, or if any of these measurements fails. Runs where nothing is flagged take as long as before, and the retest of a short benchmark takes about a minute.
node -escript in the workflow intobenchmark/compare.js, which adds the retest. The comparison table and the thresholds are unchanged.benchmark/performance.jsacceptsBENCHMARK_NAMESto run only the listed benchmarks, andBENCHMARK_ITERATIONS_FACTORto scale their iterations.base/instead of replacing it with the PR checkout, so both builds are available for the retest. The comparison and retest log are uploaded also when the check fails. The timeout goes from 30 to 45 minutes, which only matters if long-running benchmarks are retested.benchmark/compare.js. The check then fails with a message to update the branch, instead of a stack trace.An absolute floor, as suggested in #10684, was rejected: a floor that clears the observed noise of up to about 0.8 ms would let
Object.save (create)get about 2.5x slower without failing.The benchmark and comparison steps of the workflow were run for 3 benchmarks in an Ubuntu 24.04 container with Node 24.11.0,
mongodb-runnerandtaskset:Object.save (create)at +35%: the retest measured -0.9% and the check passed.Tasks
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