Reduce run filtering allocations by j178 · Pull Request #2090 · j178/prek

j178 · 2026-05-17T09:44:03Z

Reduces allocation pressure in prek run filtering by borrowing tag-cache path keys from the existing run input and avoiding full filename vector materialization for hooks with pass_filenames: false.

On the synthetic 16k-file workload used during profiling, allocator traffic dropped from about 59.9k to 43.9k allocations, and peak live heap dropped from about 5.33 MB to 2.95 MB.

codecov · 2026-05-17T09:45:40Z

Codecov Report

❌ Patch coverage is 97.59036% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.47%. Comparing base (787bda0) to head (4369a80).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/prek/src/cli/run/filter.rs	97.43%	1 Missing ⚠️
crates/prek/src/cli/run/run.rs	97.72%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2090      +/-   ##
==========================================
+ Coverage   92.34%   92.47%   +0.13%     
==========================================
  Files         119      119              
  Lines       24413    24478      +65     
==========================================
+ Hits        22545    22637      +92     
+ Misses       1868     1841      -27

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Copilot

Pull request overview

This PR reduces allocation pressure during prek run hook filtering by (1) borrowing tag-cache keys from the existing run input paths instead of allocating PathBufs, and (2) avoiding full filename collection for hooks that don’t accept filenames (pass_filenames: false / PassFilenames::None).

Changes:

Introduce HookRunInput to track “has matches” separately from the (optional) filename list, enabling early “any match?” checks without materializing vectors.
Rework FileTagCache to store tags keyed by &Path (borrowed) rather than PathBuf (owned), eliminating per-path key allocations.
Minor allocation tuning in run_hooks (pre-reserving the project→hooks map) and in ProjectFiles::for_project (conditional preallocation).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
`crates/prek/src/cli/run/run.rs`	Avoids building filename vectors for `PassFilenames::None` hooks by passing a new `HookRunInput` (match boolean + optional filenames).
`crates/prek/src/cli/run/filter.rs`	Makes `FileTagCache` borrow `&Path` keys and adds `has_match_for_hook` for match-only filtering without collecting filenames.

prek-ci-bot · 2026-05-17T09:53:29Z

📦 Cargo Bloat Comparison

Binary size change: +0.00% (26.1 MiB → 26.1 MiB)

Expand for cargo-bloat output

Head Branch Results

 File  .text     Size             Crate Name
 1.2%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_encrypt_avx512
 1.2%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_decrypt_avx512
 0.3%   0.7%  91.9KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.7%  83.8KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.5%  65.5KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.5%  61.1KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.2%   0.4%  53.3KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  48.6KiB              prek prek::run::{{closure}}
 0.2%   0.3%  43.3KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  33.3KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2%  32.1KiB             prek? <prek::config::_::<impl serde_core::de::Deserialize for prek::config::Config>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2%  28.7KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.6KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble
 0.1%   0.2%  26.2KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  23.2KiB              prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2%  22.5KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  22.3KiB         [Unknown] Lp384_montjscalarmul_alt_p384_montjadd
 0.1%   0.2%  21.5KiB      clap_builder clap_builder::parser::parser::Parser::get_matches_with
41.6%  86.3%  10.9MiB                   And 23856 smaller methods. Use -n N to show more.
48.1% 100.0%  12.6MiB                   .text section size, the file size is 26.1MiB

Base Branch Results

 File  .text     Size             Crate Name
 1.2%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_encrypt_avx512
 1.2%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_decrypt_avx512
 0.3%   0.7%  92.0KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.7%  84.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.5%  65.5KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.5%  60.9KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.2%   0.4%  53.3KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  48.6KiB              prek prek::run::{{closure}}
 0.2%   0.3%  43.8KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  33.3KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2%  32.1KiB             prek? <prek::config::_::<impl serde_core::de::Deserialize for prek::config::Config>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2%  28.7KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.6KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble
 0.1%   0.2%  26.5KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  23.9KiB              prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2%  22.5KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  22.3KiB         [Unknown] Lp384_montjscalarmul_alt_p384_montjadd
 0.1%   0.2%  21.5KiB      clap_builder clap_builder::parser::parser::Parser::get_matches_with
41.6%  86.3%  10.9MiB                   And 23840 smaller methods. Use -n N to show more.
48.2% 100.0%  12.6MiB                   .text section size, the file size is 26.1MiB

prek-ci-bot · 2026-05-17T09:53:30Z

⚡️ Hyperfine Benchmarks

Summary: 0 regressions, 1 improvements above the 10% threshold.

Environment

OS: Linux 6.17.0-1013-azure
CPU: 4 cores
prek version: prek 0.4.0+8 (88a2c9b 2026-05-17)
Rust version: rustc 1.95.0 (59807616e 2026-04-14)
Hyperfine version: hyperfine 1.20.0

CLI Commands

Benchmarking basic commands in the main repo:

`prek --version`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base --version`	2.3 ± 0.1	2.2	2.7	1.10 ± 0.06
`prek-head --version`	2.1 ± 0.1	2.0	2.3	1.00

`prek list`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base list`	9.4 ± 0.3	8.9	10.8	1.01 ± 0.08
`prek-head list`	9.3 ± 0.7	8.7	14.8	1.00

`prek validate-config .pre-commit-config.yaml`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base validate-config .pre-commit-config.yaml`	3.2 ± 0.2	3.1	4.3	1.00 ± 0.42
`prek-head validate-config .pre-commit-config.yaml`	3.2 ± 1.3	2.9	12.5	1.00

`prek sample-config`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base sample-config`	2.6 ± 0.0	2.5	2.7	1.05 ± 0.03
`prek-head sample-config`	2.4 ± 0.0	2.4	2.6	1.00

Cold vs Warm Runs

Comparing first run (cold) vs subsequent runs (warm cache):

`prek run --all-files (cold - no cache)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run --all-files`	141.0 ± 5.0	134.6	150.1	1.00 ± 0.04
`prek-head run --all-files`	141.0 ± 3.5	135.4	148.8	1.00

`prek run --all-files (warm - with cache)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run --all-files`	140.9 ± 3.0	135.0	146.3	1.01 ± 0.03
`prek-head run --all-files`	139.3 ± 3.0	133.3	145.7	1.00

Full Hook Suite

Running the builtin hook suite on the benchmark workspace:

`prek run --all-files (full builtin hook suite)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run --all-files`	140.3 ± 3.6	134.5	149.7	1.00 ± 0.03
`prek-head run --all-files`	140.2 ± 3.3	134.8	148.1	1.00

Individual Hook Performance

Benchmarking each hook individually on the test repo:

`prek run trailing-whitespace --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run trailing-whitespace --all-files`	20.7 ± 0.6	19.6	22.1	1.00
`prek-head run trailing-whitespace --all-files`	20.9 ± 0.9	19.9	23.3	1.01 ± 0.05

`prek run end-of-file-fixer --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run end-of-file-fixer --all-files`	35.0 ± 29.3	23.8	150.4	1.31 ± 1.10
`prek-head run end-of-file-fixer --all-files`	26.8 ± 1.6	24.0	29.7	1.00

✅ Performance improvement for prek run end-of-file-fixer --all-files: 23.5800% faster

`prek run check-json --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-json --all-files`	12.0 ± 0.5	11.1	13.3	1.04 ± 0.05
`prek-head run check-json --all-files`	11.6 ± 0.3	10.9	12.1	1.00

`prek run check-yaml --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-yaml --all-files`	12.1 ± 0.4	11.3	12.7	1.06 ± 0.04
`prek-head run check-yaml --all-files`	11.5 ± 0.3	10.9	12.2	1.00

`prek run check-toml --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-toml --all-files`	11.7 ± 0.3	11.2	12.5	1.02 ± 0.04
`prek-head run check-toml --all-files`	11.5 ± 0.3	11.0	12.1	1.00

`prek run check-xml --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-xml --all-files`	11.9 ± 0.5	11.2	12.8	1.00
`prek-head run check-xml --all-files`	12.0 ± 1.0	11.2	17.2	1.01 ± 0.10

`prek run detect-private-key --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run detect-private-key --all-files`	17.8 ± 1.4	15.5	20.6	1.03 ± 0.14
`prek-head run detect-private-key --all-files`	17.3 ± 2.0	15.2	25.5	1.00

`prek run fix-byte-order-marker --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run fix-byte-order-marker --all-files`	22.5 ± 1.3	20.1	25.1	1.01 ± 0.09
`prek-head run fix-byte-order-marker --all-files`	22.4 ± 1.6	19.8	25.5	1.00

Installation Performance

Benchmarking hook installation (fast path hooks skip Python setup):

`prek install-hooks (cold - no cache)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base install-hooks`	4.7 ± 0.0	4.6	4.7	1.04 ± 0.01
`prek-head install-hooks`	4.5 ± 0.0	4.5	4.5	1.00

`prek install-hooks (warm - with cache)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base install-hooks`	4.7 ± 0.1	4.6	4.9	1.05 ± 0.03
`prek-head install-hooks`	4.5 ± 0.1	4.4	4.6	1.00

File Filtering/Scoping Performance

Testing different file selection modes:

`prek run (staged files only)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run`	48.8 ± 1.3	47.2	52.0	1.01 ± 0.03
`prek-head run`	48.3 ± 0.9	47.1	50.8	1.00

`prek run --files '*.json' (specific file type)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run --files '*.json'`	8.4 ± 0.1	8.2	8.6	1.02 ± 0.02
`prek-head run --files '*.json'`	8.2 ± 0.1	8.0	8.4	1.00

Workspace Discovery & Initialization

Benchmarking hook discovery and initialization overhead:

`prek run --dry-run --all-files (measures init overhead)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run --dry-run --all-files`	11.0 ± 0.4	10.5	11.8	1.07 ± 0.04
`prek-head run --dry-run --all-files`	10.3 ± 0.2	10.1	10.7	1.00

Meta Hooks Performance

Benchmarking meta hooks separately:

`prek run check-hooks-apply --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-hooks-apply --all-files`	12.5 ± 0.1	12.3	12.7	1.00
`prek-head run check-hooks-apply --all-files`	12.9 ± 0.6	11.9	13.6	1.03 ± 0.05

`prek run check-useless-excludes --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-useless-excludes --all-files`	12.2 ± 0.2	11.9	12.6	1.08 ± 0.04
`prek-head run check-useless-excludes --all-files`	11.3 ± 0.3	10.9	11.8	1.00

`prek run identity --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run identity --all-files`	10.7 ± 0.4	10.1	11.3	1.06 ± 0.05
`prek-head run identity --all-files`	10.1 ± 0.3	9.8	10.8	1.00

This MR contains the following updates: | Package | Update | Change | |---|---|---| | [prek](https://github.com/j178/prek) | patch | `0.4.0` → `0.4.1` | MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot). **Proposed changes to behavior should be submitted there as MRs.** --- ### Release Notes <details> <summary>j178/prek (prek)</summary> ### [`v0.4.1`](https://github.com/j178/prek/blob/HEAD/CHANGELOG.md#041) [Compare Source](j178/prek@v0.4.0...v0.4.1) Released on 2026-05-20. ##### Enhancements - Fix pre-push range after rebase ([#2089](j178/prek#2089)) - Prefer extensions over loose filename tags ([#2092](j178/prek#2092)) - Skip installs for hooks that will not run ([#2103](j178/prek#2103)) ##### Performance - Optimize meta hook file scans ([#2106](j178/prek#2106)) - Reduce run filtering allocations ([#2090](j178/prek#2090)) ##### Contributors - [@j178](https://github.com/j178) </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - At any time (no schedule defined) - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this MR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this MR, check this box --- This MR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).

Copilot AI review requested due to automatic review settings May 17, 2026 09:44

Copilot started reviewing on behalf of j178 May 17, 2026 09:44 View session

j178 added the performance Performance improvements label May 17, 2026

Copilot AI reviewed May 17, 2026

View reviewed changes

Reduce run filtering allocations

4369a80

j178 force-pushed the prek-allocator branch from f186876 to 4369a80 Compare May 17, 2026 10:21

j178 merged commit 580caee into master May 17, 2026
34 checks passed

j178 deleted the prek-allocator branch May 17, 2026 10:29

BrewTestBot mentioned this pull request May 20, 2026

prek 0.4.1 Homebrew/homebrew-core#283700

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Pull request overview

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📦 Cargo Bloat Comparison

Head Branch Results

Base Branch Results

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⚡️ Hyperfine Benchmarks

prek --version

prek list

prek validate-config .pre-commit-config.yaml

prek sample-config

prek run --all-files (cold - no cache)

prek run --all-files (warm - with cache)

prek run --all-files (full builtin hook suite)

prek run trailing-whitespace --all-files

prek run end-of-file-fixer --all-files

prek run check-json --all-files

prek run check-yaml --all-files

prek run check-toml --all-files

prek run check-xml --all-files

prek run detect-private-key --all-files

prek run fix-byte-order-marker --all-files

prek install-hooks (cold - no cache)

prek install-hooks (warm - with cache)

prek run (staged files only)

prek run --files '*.json' (specific file type)

prek run --dry-run --all-files (measures init overhead)

prek run check-hooks-apply --all-files

prek run check-useless-excludes --all-files

prek run identity --all-files

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codecov Bot commented May 17, 2026 •

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`prek --version`

`prek list`

`prek validate-config .pre-commit-config.yaml`

`prek sample-config`

`prek run --all-files (cold - no cache)`

`prek run --all-files (warm - with cache)`

`prek run --all-files (full builtin hook suite)`

`prek run trailing-whitespace --all-files`

`prek run end-of-file-fixer --all-files`

`prek run check-json --all-files`

`prek run check-yaml --all-files`

`prek run check-toml --all-files`

`prek run check-xml --all-files`

`prek run detect-private-key --all-files`

`prek run fix-byte-order-marker --all-files`

`prek install-hooks (cold - no cache)`

`prek install-hooks (warm - with cache)`

`prek run (staged files only)`

`prek run --files '*.json' (specific file type)`

`prek run --dry-run --all-files (measures init overhead)`

`prek run check-hooks-apply --all-files`

`prek run check-useless-excludes --all-files`

`prek run identity --all-files`