perf: Eliminate redundant syscalls in FSCache fetch and exists#11985
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anthonyshew merged 1 commit intomainfrom Feb 24, 2026
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perf: Eliminate redundant syscalls in FSCache fetch and exists#11985anthonyshew merged 1 commit intomainfrom
anthonyshew merged 1 commit intomainfrom
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In fetch(), replace the exists() + open() two-step with a single open() attempt. Drop the legacy uncompressed .tar fallback — put() has written .tar.zst exclusively since the Go-to-Rust port in 2023. In exists(), check only .tar.zst. This reduces cache hits from 3 syscalls to 1, and cache misses from 2 syscalls to 1.
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## Release v2.8.11-canary.28 > [!NOTE] > This release PR was created manually because the [automated release workflow failed](https://github.com/vercel/turborepo/actions/runs/22396672874/job/64834751381) during the "Create Release PR" step. The npm packages were already published successfully. ### Changes - release(turborepo): 2.8.11-canary.27 (#11975) (`09e2557`) - chore: Move git hooks from pre-commit to pre-push and match CI lint checks (#11977) (`68928c0`) - chore: Update AGENTS.md (#11978) (`3887e0d`) - fix: Use correct pnpm version in library release workflow (#11979) (`716229d`) - fix: Fix library release workflow for Trusted Publishing OIDC (#11980) (`f2b57af`) - fix: Use repo setup-node action in library release package job (#11981) (`c8d6fd8`) - fix: Add repository field to @turbo/repository package.json (#11982) (`2865110`) - perf: Replace heap-allocated String with stack-allocated OidHash for git OIDs (#11984) (`24e1937`) - perf: Eliminate redundant syscalls in FSCache fetch and exists (#11985) (`ba1e3bb`) - release(library): 0.0.1-canary.19 (#11983) (`a5bc714`) - perf: Reduce per-task allocations in visitor dispatch loop (#11986) (`53b2b4f`) - docs: Fix same-page anchor links that don't scroll to target (#11989) (`b1d5ec2`) - docs: Mention inputs key in package hash inputs table (#11990) (`6bc216b`) - fix(docs): update sitemap.md to single-line pipe-delimited format (#11976) (`fd15d24`) - fix: Disable husky pre-push hook during release staging (#11991) (`2365307`) - fix: Disable husky pre-push hook in release workflow (#11992) (`71ca25c`)
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## Release v2.8.11-canary.29 Versioned docs: https://v2-8-11-canary-29.turborepo.dev ### Changes - release(turborepo): 2.8.11-canary.27 (#11975) (`09e2557`) - chore: Move git hooks from pre-commit to pre-push and match CI lint checks (#11977) (`68928c0`) - chore: Update AGENTS.md (#11978) (`3887e0d`) - fix: Use correct pnpm version in library release workflow (#11979) (`716229d`) - fix: Fix library release workflow for Trusted Publishing OIDC (#11980) (`f2b57af`) - fix: Use repo setup-node action in library release package job (#11981) (`c8d6fd8`) - fix: Add repository field to @turbo/repository package.json (#11982) (`2865110`) - perf: Replace heap-allocated String with stack-allocated OidHash for git OIDs (#11984) (`24e1937`) - perf: Eliminate redundant syscalls in FSCache fetch and exists (#11985) (`ba1e3bb`) - release(library): 0.0.1-canary.19 (#11983) (`a5bc714`) - perf: Reduce per-task allocations in visitor dispatch loop (#11986) (`53b2b4f`) - docs: Fix same-page anchor links that don't scroll to target (#11989) (`b1d5ec2`) - docs: Mention inputs key in package hash inputs table (#11990) (`6bc216b`) - fix(docs): update sitemap.md to single-line pipe-delimited format (#11976) (`fd15d24`) - fix: Disable husky pre-push hook during release staging (#11991) (`2365307`) - fix: Disable husky pre-push hook in release workflow (#11992) (`71ca25c`) - release(turborepo): 2.8.11-canary.28 (#11993) (`5793b0a`) - fix: Use versioned schema URLs in Turborepo skill files (#11994) (`7e48e24`) --------- Co-authored-by: Turbobot <turbobot@vercel.com>
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Summary
fetch(), replace theexists()+CacheReader::open()two-step with a singleopen()attempt — 1 syscall instead of 3 on cache hits.tarfallback from bothfetch()andexists()—put()has written.tar.zstexclusively since the Go-to-Rust port in mid-2023Profile data for the large repo shows
fetchself-time dropped from 200.5ms (11.8%) to 129.6ms (8.0%) — a 35% reduction across 962 calls.Benchmarks run on a Linux sandbox with hyperfine (15 runs, 2 warmup), all cache-hit scenarios.
Why
Every
fetch()call was doing:stat(.tar)→ ENOENT →stat(.tar.zst)→ OK →open(.tar.zst)— 3 syscalls. The new flow isopen(.tar.zst)→ done. The uncompressed.tarpath was a fallback for artifacts from the Go era (~2021-2022). No modern Turborepo version writes uncompressed cache artifacts, and cache entries rotate out constantly.