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Perf regression: nuget/rescan wall +31% (f3c6313a..17793173; #1340/#1341) #1425
Description
[agent] Bench: nuget/rescan wall time is +31% and nuget/hosted +28% on today's main (17793173), compared with f3c6313a (the previous bench run, 2026-10-09). Request counts are unchanged (53).
Culprit: not bisected. The candidates are the two commits in f3c6313a..17793173 that add NuGet inputs to the hosted engine's discovery and confirm step: e7d8bae4 (#1340, NuGet lock discovery for member and named locks) and ee14e7d7 (#1341, NuGet mapping exclusivity and inherited sources). 10874cc3 (#1344, the stale global-packages warning) is a third, less likely candidate.
Same-machine interleaved compare
Base f3c6313a → head 17793173, on a 4 vCPU Intel Xeon @ 2.10GHz cloud sandbox. An A/A run on the same machine was clean.
| scenario | round | base wall | head wall | Δ wall [95% CI] | Δ CPU | requests |
|---|---|---|---|---|---|---|
nuget/hosted |
1 (15+10 pairs) | 81.9 ms | 100.9 ms | +28.4% [+12.5, +34.0] | +20.0% | 53 |
nuget/hosted |
2 (20+10 pairs) | 77.9 ms | 95.7 ms | +28.2% [+20.6, +38.1] | +21.7% | 53 |
nuget/rescan |
1 | 65.1 ms | 88.9 ms | +34.5% [+24.6, +48.5] | +24.7% | 53 |
nuget/rescan |
2 | 61.9 ms | 80.8 ms | +30.7% [+24.2, +37.2] | +23.9% | 53 |
(These numbers use the bench fixture from #1422, which allows #1344's new redirect_nuget_stale_global_package warning. Without that change the head fails validation on main.)
Hot spot
Callgrind on the head binary, nuget/rescan (900 packages, 25 patched, restored project with obj/project.assets.json), inclusive instructions:
41.7% scan::hosted::run_redirect_selected_untracked
34.8% hosted::engine::confirm
34.6% patch::redirect::presence::groups_present
23.5% aho_corasick::AhoCorasick::new (automaton build, 1 call)
11.0% Automaton::try_find_overlapping (27 texts)
14.6% crawlers::nuget_crawler::parse_project_assets (4 calls: 2× restore_scope, 2× read_project_assets)
14.8% vex::discover::nuget::extract
About a third of the scan goes to groups_present, which builds a DFA and scans 27 texts. The new NuGet discovery entries (NUGET_LOCKS_KEY / inherited-sources texts, plus the extra lock files read in) now feed into it. obj/project.assets.json is also parsed into a serde_json::Value four times per scan.
Repro
export CARGO_PROFILE_PERF_INHERITS=release CARGO_PROFILE_PERF_LTO=thin CARGO_PROFILE_PERF_STRIP=none
git worktree add /tmp/base f3c6313a && (cd /tmp/base && CARGO_TARGET_DIR=/tmp/tb cargo build --locked --profile perf -p socket-patch-cli)
CARGO_TARGET_DIR=/tmp/th cargo build --locked --profile perf -p socket-patch-cli -p socket-patch-bench
/tmp/th/perf/socket-patch-bench compare --base /tmp/tb/perf/socket-patch --head /tmp/th/perf/socket-patch -f '^nuget/' --runs 20Runner: nproc 4, Intel(R) Xeon(R) Processor @ 2.10GHz.
Generated by Claude Code
Activity
mikolalysenko commentedon Oct 12, 2026
[agent] Bench: context from the weekly A/B in the same run. Base
045d7ec7(2026-10-05) → head17793173, 8+8 pairs:nuget/hostedis -1.7% andnuget/rescanis +3.9%, both ≈. Between045d7ec7andf3c6313a, #1183 (the restore-scoped crawl) made the NuGet scans 13–21% faster. This regression gives most of that gain back, so the fix target is thef3c6313alevel (≈62–78 ms on this runner), not the week-old one.Generated by Claude Code