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vercel__workflow/.github/scripts/render-benchmark-comment.mjs
Shalabh Chaturvedi 8bda7cef79 [benchmarks] Split STSO by inline vs queue-hop steps, add distribution diffs vs main (#3213)
* Split STSO by inline vs queue-hop steps, add distribution diffs vs main

The sequential-steps benchmark's STSO metric mixed two unrelated
phenomena: gaps between steps running back-to-back in the same warm
process, and gaps across an invocation boundary (queue dispatch, client
reinit, event-log replay), which cost ~10x more. The old step-index
windows (1-20 / 101-120 / 1001-1020) sampled 19 gaps each and captured
neither cleanly: whether a boundary happened to land inside a window
moved that window's P99 by hundreds of percent, which is most of the
run-to-run variance the benchmark comment was reporting.

The workflow now tags each step with whether it was the first step body
executed in its process ('queue-hop') or a later one in the same warm
process ('inline') via a process-global, so the split is ground truth
rather than inferred from step index or trace timestamps. STSO is
reported as two rows over *every* gap in the run instead of three
sampled windows. No targets on the new rows — the old ones described the
index-bucketed grouping.

computeStats now keeps the full sorted sample array alongside the
percentiles, and the comment renders a histogram + cumulative-time diff
against `main` under the table, one per STSO kind. Percentiles alone
hide how many samples moved and by how much, which is exactly where the
variance lives. Inline rows use a fixed 50ms bin width (the adaptive
width is coarse enough to hide structure inside that cluster); queue-hop
rows keep the adaptive width. Negative gaps (clock skew between two step
bodies' clocks) get their own bucket rather than being counted with the
slow tail.

Raw samples are stripped from the comment's embedded data block — ~1000
per run would exceed GitHub's comment size limit within a couple of
history entries — so the histogram renders for the current run only,
while collapsed history keeps its tables. Until this lands on `main` no
baseline has raw samples, so the section renders this run's distribution
as a single series.

Co-Authored-By: shalabhc <shalabh.chaturvedi@vercel.com>

* Clarify what stripping raw samples from the data block does not affect

Co-Authored-By: shalabhc <shalabh.chaturvedi@vercel.com>

* Drop the bucket tables; fold counts and deltas into the histogram bars

Co-Authored-By: shalabhc <shalabh.chaturvedi@vercel.com>

* Collapse the STSO distribution section into a dropdown

Co-Authored-By: shalabhc <shalabh.chaturvedi@vercel.com>

* Fix footer assertion after the dropdown wording change

Co-Authored-By: shalabhc <shalabh.chaturvedi@vercel.com>

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Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
2026-07-30 13:38:25 -07:00

30 KiB