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perf(ci): balance extended-suite shards by measured duration, not count - #1546
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Included review availability: Your plan provides up to 2 included reviews per hour; 0 remain after this review. 📝 WalkthroughWalkthroughThe CI workflow replaces positional extended-suite sharding with deterministic greedy balancing. It uses measured suite durations, defaults invalid or missing weights to 30 seconds, sorts suites by duration, and assigns each suite to one of four shards. ChangesExtended-suite sharding
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to This change rebalances CI suite assignment by measured duration without changing product runtime behavior; no actionable merge-blocking risk remains. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
Full details: Docstring CoverageExplanation No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.) ✨ Finishing Touches🧪 Generate unit tests (beta)
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In @.github/workflows/ci.yml:
- Around line 851-855: Reorder the SUITES entries so all weight-4 suites,
including test:codex@4, test:credentials@4, test:music:unit@4, and
test:stt:unit@4, appear before test:avatar:unit@3. Preserve the existing suite
names and weights.
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In @.github/workflows/ci.yml:
- Around line 890-891: Update the weight extraction in the loop over SORTED so
validated weights are interpreted as decimal before any arithmetic, using the
existing w variable and preserving support for values such as 08 and 010.
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Sharding by position in the list balances the NUMBER of suites per shard.
That is the wrong quantity. Measured per-suite wall-clock from run
32808851519, parsed from the ::group:: timestamps in all four shard logs:
test:tts:unit 367s
test:vertex-loop-characterization 96s
test:tool-reliability 51s
test:auth 45s
test:vertex-claude-characterization 45s
...24 further suites 170s combined
-----
774s across 28 suites
A 1s-to-367s spread means equal counts give wildly unequal shards. Observed:
shard 1 108s shard 2 36s shard 3 486s shard 4 150s
Shard 3 was 13x shard 2 and, at 8.1m, the longest job in the CI workflow.
Each runner now walks the same longest-first list and gives every suite to
whichever shard is currently least loaded — greedy longest-processing-time.
All four compute the identical assignment independently, with no coordination,
because the input list and the traversal order are the same everywhere.
Verified by extracting the actual shell out of the workflow and running it
under `bash -e`:
shard 1: 1 suite, 367s
shard 2: 8 suites, 137s
shard 3: 10 suites, 136s
shard 4: 9 suites, 136s
28 distinct suites, none duplicated, none dropped
critical path 486s -> 367s (8.1m -> 6.1m)
Entries are normalised to name@weight and sorted by weight descending at
runtime. LPT requires longest-first input, and sorting in the workflow makes
that a property of the code rather than of how carefully the list above was
maintained — the first draft had test:avatar:unit@3 sitting above four @4
entries, which happened not to change the result but would have silently
degraded balance after any later weight edit. Verified by shuffling the list
so the shortest suite comes first: the assignment is byte-identical.
Weights affect BALANCE ONLY. A stale weight makes one shard slower; it can
never cause a suite to be skipped or run twice, because assignment is a
partition of the list rather than a filter over it. An entry with no @weight,
or with a non-numeric one, is assigned an assumed 30s and still runs — both
paths verified.
if/fi replaces `[ ] && { }` for the comparisons. These steps run under
`bash -e`, where a false test in an AND-OR list can abort the step, and a
comparison that is merely false is not an error here.
Two honest limits on the benefit.
367s is a floor, not a result: test:tts:unit alone exceeds the 194s that a
perfect four-way split would give, so no assignment can do better while it
costs that much. 240s of those 367s are a single test that deadlocks and is
reported as skipped rather than failed, which is tracked separately; if that
is fixed, the same scheme here yields roughly 2.2m with no further change.
And extended-suites is non-blocking. This does not move time-to-mergeable,
which is 5.8m and set by provider-safety-net, nor time-to-all-green, which is
20.5m and set by Yama PR Review. It shortens the CI workflow itself and
reduces runner time.
Weights are forced to base 10 with 10#. Bash reads a leading zero as octal,
so a weight of 08 aborts the step outright ("value too great for base") and
010 silently becomes 8 — the quiet one is the worse failure, since it just
unbalances the shards with nothing to notice. The digit guard accepts both
forms, and sort -n already normalises them, so only the arithmetic needed it.
Verified by adding @08 and @010 entries to the simulation: exit 0, weights 8
and 10, real assignment unchanged.
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test:tts:unit still declared 367s. The deadlock fix in #1550 landed 33 seconds after #1546 measured it, and cut the suite to a CI median of 140s — a 2.6x overstatement that survived because nothing re-measures. Five weights are refreshed from the median of 13 runs, read out of this job's own logs via the timestamps on its ::group:: markers. Scoring both plans against the measured durations, over the 34 suites now in the list: planned shard loads go from 367/179/179/178 to 172/172/172/172, and the spread across shards from 189s to 0s. The worst shard halves, 367s to 172s. Almost all of that comes from tts:unit alone: at a declared 367s it exceeded the ideal quarter-share outright, so LPT had no choice but to give it a shard to itself and let the other three carry everything else. An earlier draft of this message reported the gain as "worst shard 145s -> 141s, about four seconds", and paired a 367/137/136/136 row with a spread of 11s. Those two figures came from different datasets — the first row is the old plan's self-declared sums, whose own spread is 231s, while the 11s was the old grouping re-scored against the new weights. Neither described the list as it now stands. The numbers above are recomputed with the workflow's own LPT loop against the list in this commit. Verified with that assignment loop, extracted verbatim rather than reimplemented: all 34 suites assigned, each exactly once. The suite set is unchanged; only the numbers move. Weights affect balance only, never which suites run. The comment now says how to re-measure, because the root cause here is that nobody could. The recipe it replaces did not work: it bound the timestamp only at ::group::, never read the ::endgroup:: one, and so printed a start time and a `##[group]`-prefixed name instead of a duration. The version here prints `suite@seconds`, pastes straight into the list, avoids gawk's mktime() so it runs on BSD awk, and was executed against a captured log before being written down. Two traps are written down with it. Do not time these locally: a developer machine is faster than a runner and has credentials, so suites that skip in CI do real work. test:tts:unit measures ~73s locally against a CI median of 140s — wrong by nearly half, and wrong in the direction that makes the imbalance look worse than it is. And take a median across runs rather than one sample: test:tts:unit alone spans 95s to 155s, so a single observation can be off by 40%. test:tool-reliability and test:autoresearch are weighted at their skip times, which is correct for this job — it has no credentials — and wrong to reuse anywhere that runs them for real. That is now stated next to them.
murdore
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Aug 29, 2026
test:tts:unit still declared 367s. The deadlock fix in #1550 landed 33 seconds after #1546 measured it, and cut the suite to a CI median of 140s — a 2.6x overstatement that survived because nothing re-measures. Five weights are refreshed from the median of 13 runs, read out of this job's own logs via the timestamps on its ::group:: markers. Scoring both plans against the measured durations, over the 38 suites in the list as of this commit: planned shard loads go from 367/221/221/221 to 204/204/204/203, and the spread across shards from 146s to 1s. The worst shard drops from 367s to 204s. Almost all of that comes from tts:unit alone: at a declared 367s it exceeded the ideal quarter-share outright, so LPT had no choice but to give it a shard to itself and let the other three carry everything else. These figures are a property of the list, not of this change, so they move whenever a suite is added. Recompute rather than trusting them: the weights here are what was measured, and the shard arithmetic follows from whatever the list happens to contain on the day. An earlier draft of this message reported the gain as "worst shard 145s -> 141s, about four seconds", and paired a 367/137/136/136 row with a spread of 11s. Those two figures came from different datasets — the first row is the old plan's self-declared sums, whose own spread is 231s, while the 11s was the old grouping re-scored against the new weights. Neither described the list as it now stands. The numbers above are recomputed with the workflow's own LPT loop against the list in this commit. Verified with that assignment loop, extracted verbatim rather than reimplemented: all 38 suites assigned, each exactly once. The suite set is unchanged; only the numbers move. Weights affect balance only, never which suites run. The comment now says how to re-measure, because the root cause here is that nobody could. The recipe it replaces did not work: it bound the timestamp only at ::group::, never read the ::endgroup:: one, and so printed a start time and a `##[group]`-prefixed name instead of a duration. The version here prints `suite@seconds`, pastes straight into the list, avoids gawk's mktime() so it runs on BSD awk, and was executed against a captured log before being written down. Two traps are written down with it. Do not time these locally: a developer machine is faster than a runner and has credentials, so suites that skip in CI do real work. test:tts:unit measures ~73s locally against a CI median of 140s — wrong by nearly half, and wrong in the direction that makes the imbalance look worse than it is. And take a median across runs rather than one sample: test:tts:unit alone spans 95s to 155s, so a single observation can be off by 40%. test:tool-reliability and test:autoresearch are weighted at their skip times, which is correct for this job — it has no credentials — and wrong to reuse anywhere that runs them for real. That is now stated next to them.
murdore
added a commit
that referenced
this pull request
Aug 29, 2026
test:tts:unit still declared 367s. The deadlock fix in #1550 landed 33 seconds after #1546 measured it, and cut the suite to a CI median of 140s — a 2.6x overstatement that survived because nothing re-measures. Five weights are refreshed from the median of 13 runs, read out of this job's own logs via the timestamps on its ::group:: markers. Scoring both plans against the measured durations, over the 38 suites in the list as of this commit: planned shard loads go from 367/221/221/221 to 204/204/204/203, and the spread across shards from 146s to 1s. The worst shard drops from 367s to 204s. Almost all of that comes from tts:unit alone: at a declared 367s it exceeded the ideal quarter-share outright, so LPT had no choice but to give it a shard to itself and let the other three carry everything else. These figures are a property of the list, not of this change, so they move whenever a suite is added. Recompute rather than trusting them: the weights here are what was measured, and the shard arithmetic follows from whatever the list happens to contain on the day. An earlier draft of this message reported the gain as "worst shard 145s -> 141s, about four seconds", and paired a 367/137/136/136 row with a spread of 11s. Those two figures came from different datasets — the first row is the old plan's self-declared sums, whose own spread is 231s, while the 11s was the old grouping re-scored against the new weights. Neither described the list as it now stands. The numbers above are recomputed with the workflow's own LPT loop against the list in this commit. Verified with that assignment loop, extracted verbatim rather than reimplemented: all 38 suites assigned, each exactly once. The suite set is unchanged; only the numbers move. Weights affect balance only, never which suites run. The comment now says how to re-measure, because the root cause here is that nobody could. The recipe it replaces did not work: it bound the timestamp only at ::group::, never read the ::endgroup:: one, and so printed a start time and a `##[group]`-prefixed name instead of a duration. The version here prints `suite@seconds`, pastes straight into the list, avoids gawk's mktime() so it runs on BSD awk, and was executed against a captured log before being written down. Two traps are written down with it. Do not time these locally: a developer machine is faster than a runner and has credentials, so suites that skip in CI do real work. test:tts:unit measures ~73s locally against a CI median of 140s — wrong by nearly half, and wrong in the direction that makes the imbalance look worse than it is. And take a median across runs rather than one sample: test:tts:unit alone spans 95s to 155s, so a single observation can be off by 40%. test:tool-reliability and test:autoresearch are weighted at their skip times, which is correct for this job — it has no credentials — and wrong to reuse anywhere that runs them for real. That is now stated next to them.
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Sharding by list position balances the number of suites per shard. That is the wrong quantity.
Measured per-suite wall-clock from run
32808851519, parsed from::group::timestamps across all four shard logs — 774s total across 28 suites, spread from 1s to 367s:test:tts:unittest:vertex-loop-characterizationtest:tool-reliabilitytest:authtest:vertex-claude-characterizationEqual counts therefore gave wildly unequal shards:
Shard 3 was 13× shard 2 and, at 8.1m, the longest job in the CI workflow.
Change
Each runner walks the same longest-first list and gives every suite to whichever shard is currently least loaded — greedy longest-processing-time. All four runners compute an identical assignment with no coordination, because the list and the traversal order are the same everywhere.
Verification
I extracted the actual shell out of the workflow and ran it under
bash -e:Weights affect balance only. Assignment is a partition of the list, not a filter over it, so a stale weight makes a shard slower but can never cause a suite to be skipped or run twice. An entry with no
@weight, or a non-numeric one, gets an assumed 30s and still runs — both paths verified.if/fireplaces[ ] && { }for the comparisons: these steps run underbash -e, where a false test in an AND-OR list can abort the step, and a merely-false comparison is not an error here.Two honest limits
367s is a floor, not a result.
test:tts:unitalone exceeds the 194s a perfect four-way split would give, so no assignment beats it while that suite costs this much. 240s of those 367s are a single test that deadlocks and is reported as skipped rather than failed — tracked separately. Fix that and this same scheme yields ~2.2m with no further change here.extended-suitesis non-blocking. This does not move time-to-mergeable (5.8m, set byprovider-safety-net) nor time-to-all-green (20.5m, set byYama PR Review). It shortens the CI workflow itself and reduces runner time.Summary by CodeRabbit