perf: Reduce per-package hashing overhead and eliminate SCM subprocesses#11942
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anthonyshew merged 2 commits intomainfrom Feb 20, 2026
Merged
perf: Reduce per-package hashing overhead and eliminate SCM subprocesses#11942anthonyshew merged 2 commits intomainfrom
anthonyshew merged 2 commits intomainfrom
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The tests that are failing are flakes. Merging past. |
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## Release v2.8.11-canary.16 Versioned docs: https://v2-8-11-canary-16.turborepo.dev ### Changes - release(turborepo): 2.8.11-canary.15 (#11943) (`ef6dfd2`) - perf: Reduce per-package hashing overhead and eliminate SCM subprocesses (#11942) (`fc19b66`) --------- Co-authored-by: Turbobot <turbobot@vercel.com>
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Summary
Follow-up to #11938. Targets the per-package hashing hot path that dominates at scale, plus eliminates the last two git subprocesses from
--dryruns.Small repo (~6 packages)
Medium repo (~120 packages)
Large repo (~1000 packages)
The small repo results best isolate the fixed-cost improvements (git2 for branch/SHA, reduced allocation overhead) since per-package work is minimal. At larger scales, the improvements are present but within noise because wall-clock time is already well-parallelized across rayon threads.
Benchmarks
All benchmarks:
turbo run <task> --skip-infer --dry, 5 warmup + 10 measured runs, release build.Changes
FileHashes: HashMap to sorted Vec —
FileHashesinner type changed fromHashMapto pre-sortedVec. Eliminates HashMap construction (hashing, bucket allocation, rehashing) in the per-package hashing pipeline and removes redundant re-sorting in Cap'n Proto serialization. The sort happens once at the construction boundary; downstream consumers (expanded_inputs,.hash()) get pre-sorted data for free.Status entry binary search —
get_package_hashesnow usespartition_pointon pre-sorted status entries instead of a linear scan. Reduces per-package status lookup from O(dirty_files) to O(log(dirty_files) + matched). Also addswith_capacityto the per-package HashMap to avoid rehashing.git2 for branch/SHA —
get_current_branchandget_current_sha(called bySCMState::getinto_summary) now usegit2::Repositoryinstead of forkinggit branch --show-currentandgit rev-parse HEAD. Gated behind#[cfg(feature = "git2")]with subprocess fallback.