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perf(source): Don't du on every git source load #14252

Merged
merged 1 commit into from
Jul 15, 2024
Merged

perf(source): Don't du on every git source load #14252

merged 1 commit into from
Jul 15, 2024

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epage
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@epage epage commented Jul 15, 2024

What does this PR try to resolve?

When profiling Zed (#14238), a major factor in their no-op run times is git patches and git dependencies. The slowest operation for each git source is running du. This is extraneous for a couple of reasons

  • GC isn't stable, slowing people down for a feature they aren't using
  • Size tracking was expected to be lazy, only reading sizes when the GC is configured for size, while this was eager
  • Git checkouts are immutable but we check on every load
  • This optimized for "while filesystem caches are warm" from a checkout operation when checkout operations are rare compared to all of the other commands run on a working directory.

This removes the du, relying on the lazy loading that happens in update_null_sizes.

For Zed, this removed about 40ms total from the runtime. While by itself, this is below the threshold of being noticed,

  • It adds up if any editor integrations are calling cargo metadata a lot
  • Over time, small gains like this will add up

How should we test and review this PR?

Additional information

cc @ehuss

@epage
perf(source): Don't du on every git source load
cd74470 
When profiling Zed (rust-lang#14238), a major factor in their no-op run times
is git patches and git dependencies.  The slowest operation for each git
source is running `du`.  This is extraneous for a couple of reasons
- GC isn't stable, slowing people down for a feature they aren't using
- Size tracking was expected to be lazy, only reading sizes when the GC
  is configured for size, while this was eager
- Git checkouts are immutable but we check on every load
- This optimized for "while filesystem caches are warm" from a checkout
  operation when checkout operations are rare compared to all of the other
  commands run on a working directory.

This removes the `du`, relying on the lazy loading that happens in
`update_null_sizes`.
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rustbot commented Jul 15, 2024

r? @weihanglo

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@rustbot rustbot added A-git Area: anything dealing with git S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 15, 2024
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ehuss commented Jul 15, 2024

Seems good. I don't recall, but it looks like this was not working as intended. It should have only run du when the checkout was created, not every time it was loaded. I think it's fine to move forward with this. If we ever want to optimize for size, we can always consider a different approach.

@bors r+

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bors commented Jul 15, 2024

📌 Commit cd74470 has been approved by ehuss

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 15, 2024
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bors commented Jul 15, 2024

⌛ Testing commit cd74470 with merge a2d45dc...

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bors commented Jul 15, 2024

☀️ Test successful - checks-actions
Approved by: ehuss
Pushing a2d45dc to master...

@bors bors merged commit a2d45dc into rust-lang:master Jul 15, 2024
22 checks passed
@epage epage deleted the du-less branch July 15, 2024 18:27
@weihanglo weihanglo mentioned this pull request Jul 17, 2024
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Jul 17, 2024
@bors
Auto merge of rust-lang#127838 - weihanglo:update-cargo, r=weihanglo
cb12b52 
Update cargo

31 commits in 154fdac39ae9629954e19e9986fd2cf2cdd8d964..a2b58c3dad4d554ba01ed6c45c41ff85390560f2
2024-07-07 01:28:23 +0000 to 2024-07-16 00:52:02 +0000
- chore(ci): bump CI tools (rust-lang/cargo#14257)
- test: migrate fetch and list_availables to snapbox (rust-lang/cargo#14214)
- chore: downgrade to jobserver@0.1.28 (rust-lang/cargo#14254)
- perf(source): Don't `du` on every git source load (rust-lang/cargo#14252)
- fix(source): Don't warn about unreferenced duplicate packages (rust-lang/cargo#14239)
- feat(test): Add cargo_test to test-support prelude (rust-lang/cargo#14243)
- Add workflow to publish Cargo automatically (rust-lang/cargo#14202)
- test: migrate implicit_features to snapbox (rust-lang/cargo#14245)
- test: migrate build-std/main to snapbox (rust-lang/cargo#14241)
- test: migrate check_cfg to snapbox (rust-lang/cargo#14235)
- refactor(source): More RecursivePathSource clean up (rust-lang/cargo#14231)
- Add more profiling traces (rust-lang/cargo#14238)
- fix(overrides): Don't warn on duplicate packages from using '..' (rust-lang/cargo#14234)
- fix(test): Redact elapsed time in the minutes time frame (rust-lang/cargo#14233)
- test: Migrate lto tests to snapbox (rust-lang/cargo#14209)
- fix: Ensure dep/feature activates the dependency on 2024 (rust-lang/cargo#14221)
- chore(docs): update index of reference (rust-lang/cargo#14228)
- test: migrate test to snapbox (rust-lang/cargo#14226)
- chore: remove duplicate words (rust-lang/cargo#14229)
- docs(contrib): Document things I look for in RFCs (rust-lang/cargo#14222)
- docs(ref): Note MSRV for features in the docs (rust-lang/cargo#14224)
- test(progress): Resolve flakiness (rust-lang/cargo#14223)
- fix(test): Reduce over-prescription to the caller (rust-lang/cargo#14217)
- refactor: move get_source_id out of registry (rust-lang/cargo#14218)
- fix: rename to `rustdoc::broken_intra_doc_links` (rust-lang/cargo#14215)
- test: migrate member_errors, multitarget and new to snapbox (rust-lang/cargo#14210)
- test: migrate generate_lockfile and glob_targets to snapbox (rust-lang/cargo#14200)
- test: Ensure --list test works with cargo-bloat (rust-lang/cargo#14213)
- dont make new constant InternedString in hot path (rust-lang/cargo#14211)
- Fix compatible_with_older_cargo test. (rust-lang/cargo#14212)
- test: migrate metabuild, metadata and net_config to snapbox (rust-lang/cargo#14162)
@rustbot rustbot added this to the 1.81.0 milestone Jul 17, 2024
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