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Perf regression: yarn-berry/rescan wall +21% (a43cf327..17793173; #1321/#1323/#1397 candidates) #1607
Description
[agent] Bench: confirmed weekly regression in yarn-berry/rescan.
Base cc938aa6 (main, 2026-10-09) → head 657fce2b (main, 2026-10-15). Same machine, interleaved pairs. Daily A/B (e76cb9b3 → 657fce2b) is +4.8% [+1.8, +10.6] ≈, so this is drift that is already on main.
| scenario | pairs | base wall | head wall | Δ wall [95% CI] | Δ CPU | Δ peak RSS | requests | verdict |
|---|---|---|---|---|---|---|---|---|
yarn-berry/rescan (round 1) |
15+10 | 265.1 ms | 321.4 ms | +18.5% [+12.2, +31.3] | +14.6% | +5.6% | 127 | regression |
yarn-berry/rescan (confirm) |
25+15 | 265.9 ms | 319.1 ms | +21.4% [+13.8, +25.1] | +15.7% | +5.4% | 127 | regression |
yarn-berry/hosted (round 1) |
15 | 335.5 ms | 349.9 ms | +6.8% [-1.6, +10.9] | +9.1% | +4.9% | 127 | ≈ |
Request counts are unchanged. The 2026-10-12 daily run already saw yarn-berry/rescan +15.4% (f3c6313a..17793173), below the 20% gate at the time.
Bisect (3 builds over the 151 commits cc938aa6..17793173, 15 pairs each vs cc938aa6):
| build | Δ wall |
|---|---|
1438b1a7 (#1356) |
-0.0% [-8.2, +7.8] ≈ |
a43cf327 (#1332) |
+0.8% [-3.0, +14.2] ≈ |
eca5d247 (#1330) |
+10.0% [-0.6, +14.9] |
657fce2b (today) |
+21.4% |
So about half lands in a43cf327..eca5d247 (19 commits). The berry candidates there are a0730bb2 (#1321, retire berry resolutions left by yarn remove) and 92e001a0 (#1323, read the berry restore registry like yarn does). The rest lands in eca5d247..17793173, where 1fb8901a (#1397, berry hosted pin beside a later registry entry) is the berry-specific candidate. Not narrowed further: the bisect budget is spent.
Repro
export CARGO_PROFILE_PERF_INHERITS=release CARGO_PROFILE_PERF_LTO=thin CARGO_PROFILE_PERF_STRIP=none
git worktree add /tmp/base cc938aa6 && (cd /tmp/base && CARGO_TARGET_DIR=/tmp/tb cargo build --locked --profile perf -p socket-patch-cli)
cargo build --locked --profile perf -p socket-patch-cli -p socket-patch-bench
target/perf/socket-patch-bench compare --base /tmp/tb/perf/socket-patch --head target/perf/socket-patch -f '^yarn-berry/rescan$' --runs 25Runner: 4 vCPU, Intel(R) Xeon(R) Processor @ 2.80GHz (cloud sandbox). A/A on the same runner was clean.
Progress log: #575
Generated by Claude Code
Activity
mikolalysenko commentedon Oct 16, 2026
[agent] Triaged as
priority:p1(yarn berry, npm family; perf regression). Not a duplicate of the other open bench issues (#1570 vlt, #1473 poetry, #1606 bun): the bisect points at different berry-specific commits (#1321, #1323, #1397). No open PR addresses it. Ranked below the open correctness bugs in this tier.Generated by Claude Code