rust-lang · lqd · Jun 30, 2026 · Jun 30, 2026
diff --git a/triage/2026/2026-06-29.md b/triage/2026/2026-06-29.md
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+# 2026-06-29 Triage Log
+
+Overall, the week was fairly neutral, with no meaningful shift on most benchmarks on any of our statistics.
+
+Triage done by **@simulacrum**.
+Revision range: [8b6558a0..7dc2c162](https://perf.rust-lang.org/?start=8b6558a02b2774acfb25cf15e199467c37ba7490&end=7dc2c162b9c197aaa76a6f9e7534569537830a01&absolute=false&stat=instructions%3Au)
+
+**Summary**:
+
+| (instructions:u)                   | mean  | range           | count |
+|:----------------------------------:|:-----:|:---------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 0.9%  | [0.1%, 3.7%]    | 45    |
+| Regressions ❌ <br /> (secondary)  | 0.9%  | [0.0%, 8.0%]    | 74    |
+| Improvements ✅ <br /> (primary)   | -0.4% | [-1.4%, -0.2%]  | 34    |
+| Improvements ✅ <br /> (secondary) | -4.0% | [-30.6%, -0.2%] | 57    |
+| All ❌✅ (primary)                 | 0.3%  | [-1.4%, 3.7%]   | 79    |
+
+
+2 Regressions, 1 Improvement, 7 Mixed; 5 of them in rollups
+34 artifact comparisons made in total
+
+#### Regressions
+
+Rollup of 13 pull requests [#158487](https://github.com/rust-lang/rust/pull/158487) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=cb41b6d3daa0c1ad088a8802a6d8700c61290865&end=13f1859f2faf97a15664e655624baa7417fdc100&stat=instructions:u)
+
+| (instructions:u)                   | mean | range        | count |
+|:----------------------------------:|:----:|:------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 0.3% | [0.2%, 0.5%] | 8     |
+| Regressions ❌ <br /> (secondary)  | 0.4% | [0.2%, 0.6%] | 18    |
+| Improvements ✅ <br /> (primary)   | -    | -            | 0     |
+| Improvements ✅ <br /> (secondary) | -    | -            | 0     |
+| All ❌✅ (primary)                 | 0.3% | [0.2%, 0.5%] | 8     |
+
+Root cause is Update doc_cfg hide/show syntax
+[#157871](https://github.com/rust-lang/rust/pull/157871). Probably worth some
+follow-up since it affects lots of doc benchmarks, and at least a glance it
+seems plausible this might have a simple fix (syntax changes don't feel like
+they should be meaningfully more expensive, especially in code that doesn't use
+this feature like `helloworld`).
+
+resolve: Explicit Set for detecting resolution cycles [#158035](https://github.com/rust-lang/rust/pull/158035) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=7dc2c162b9c197aaa76a6f9e7534569537830a01&end=096694416a41840709140eb0fd0ca193d1a3e6ba&stat=instructions:u)
+
+| (instructions:u)                   | mean | range        | count |
+|:----------------------------------:|:----:|:------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 0.2% | [0.1%, 0.3%] | 7     |
+| Regressions ❌ <br /> (secondary)  | 0.4% | [0.3%, 0.6%] | 12    |
+| Improvements ✅ <br /> (primary)   | -    | -            | 0     |
+| Improvements ✅ <br /> (secondary) | -    | -            | 0     |
+| All ❌✅ (primary)                 | 0.2% | [0.1%, 0.3%] | 7     |
+
+This primarily (outside incremental) affects unused-warnings, which is a stress
+test for this code. It's expected that this change would be a slight
+regression, but per the PR description, this unblocks parallelization of this
+code, which is an important benefit.
+
+#### Improvements
+
+Rework lint pass running [#158239](https://github.com/rust-lang/rust/pull/158239) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=73100eefe2afb831c4964f579c95beeb27b86e28&end=973ad0d0ab149bde2e96422833c1265c7a5be217&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range          | count |
+|:----------------------------------:|:-----:|:--------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | -     | -              | 0     |
+| Regressions ❌ <br /> (secondary)  | -     | -              | 0     |
+| Improvements ✅ <br /> (primary)   | -0.3% | [-0.9%, -0.1%] | 16    |
+| Improvements ✅ <br /> (secondary) | -0.5% | [-1.0%, -0.2%] | 30    |
+| All ❌✅ (primary)                 | -0.3% | [-0.9%, -0.1%] | 16    |
+
+#### Mixed
+
+ GVN: Don't assume nested shared references are read-only. [#157346](https://github.com/rust-lang/rust/pull/157346) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=d29dae8d17abb191a24f57eb00f68ebc1b168314&end=91fe22da8084a1c9e993d78d4a56f22ab8396236&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range          | count |
+|:----------------------------------:|:-----:|:--------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 0.3%  | [0.1%, 0.5%]   | 9     |
+| Regressions ❌ <br /> (secondary)  | 0.3%  | [0.1%, 0.4%]   | 11    |
+| Improvements ✅ <br /> (primary)   | -0.3% | [-0.4%, -0.2%] | 10    |
+| Improvements ✅ <br /> (secondary) | -0.5% | [-1.1%, -0.2%] | 5     |
+| All ❌✅ (primary)                 | 0.0%  | [-0.4%, 0.5%]  | 19    |
+
+Soundness fix, regressions are minor.
+
+Rollup of 35 pull requests [#158342](https://github.com/rust-lang/rust/pull/158342) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=8e25b4121d5ea29bef166b86173fb043782ffbff&end=73100eefe2afb831c4964f579c95beeb27b86e28&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range          | count |
+|:----------------------------------:|:-----:|:--------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 0.1%  | [0.1%, 0.1%]   | 7     |
+| Regressions ❌ <br /> (secondary)  | 0.7%  | [0.1%, 1.0%]   | 6     |
+| Improvements ✅ <br /> (primary)   | -0.3% | [-0.5%, -0.1%] | 5     |
+| Improvements ✅ <br /> (secondary) | -0.1% | [-0.2%, -0.1%] | 3     |
+| All ❌✅ (primary)                 | -0.1% | [-0.5%, 0.1%]  | 12    |
+
+* Improvements are fully from proc_macro simplification [#157271](https://github.com/rust-lang/rust/pull/157271)
+* Regressions are from:
+  * delegation: add support for infers in generics [#157960](https://github.com/rust-lang/rust/pull/157960)
+    * fixed in delegation: store child segment flag in PathSegment [#158556](https://github.com/rust-lang/rust/pull/158556)
+  * Possibly some other PRs; note that there is also some regressions in ctfe-stress that I suspect are noise.
+
+Add rigid alias marker [#156742](https://github.com/rust-lang/rust/pull/156742) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=973ad0d0ab149bde2e96422833c1265c7a5be217&end=fa36a479e492137fdf473a891206da127f132910&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range           | count |
+|:----------------------------------:|:-----:|:---------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 1.0%  | [0.3%, 2.1%]    | 22    |
+| Regressions ❌ <br /> (secondary)  | 1.2%  | [0.3%, 3.6%]    | 13    |
+| Improvements ✅ <br /> (primary)   | -0.1% | [-0.1%, -0.1%]  | 3     |
+| Improvements ✅ <br /> (secondary) | -6.0% | [-30.9%, -0.1%] | 31    |
+| All ❌✅ (primary)                 | 0.8%  | [-0.1%, 2.1%]   | 25    |
+
+> necessary refactor for the new trait solver and I would just eat the 1.4% diesel regression. 
+
+(see more here: https://github.com/rust-lang/rust/pull/156742#issuecomment-4807181842)
+
+Rollup of 15 pull requests [#158416](https://github.com/rust-lang/rust/pull/158416) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=fa36a479e492137fdf473a891206da127f132910&end=bd08c9e71874a81670fe3938dbf85148e42c2b96&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range          | count |
+|:----------------------------------:|:-----:|:--------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 0.1%  | [0.1%, 0.1%]   | 1     |
+| Regressions ❌ <br /> (secondary)  | -     | -              | 0     |
+| Improvements ✅ <br /> (primary)   | -0.2% | [-0.4%, -0.1%] | 2     |
+| Improvements ✅ <br /> (secondary) | -     | -              | 0     |
+| All ❌✅ (primary)                 | -0.1% | [-0.4%, 0.1%]  | 3     |
+
+Non-instruction count wins from reverting a change to how we build LLVM which
+broke PGO. Minor regressions/wins otherwise that are *maybe* within noise
+threshold, not worth digging deeper.
+
+Rollup of 15 pull requests [#158455](https://github.com/rust-lang/rust/pull/158455) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=ce9954c0cfc4bf26b82aef16e6fd8b020c237992&end=16761606d606b6ec4d0c88fc9251670742ad9fd2&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range          | count |
+|:----------------------------------:|:-----:|:--------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 0.1%  | [0.1%, 0.1%]   | 2     |
+| Regressions ❌ <br /> (secondary)  | 0.2%  | [0.1%, 0.2%]   | 6     |
+| Improvements ✅ <br /> (primary)   | -0.2% | [-0.2%, -0.2%] | 1     |
+| Improvements ✅ <br /> (secondary) | -0.3% | [-0.5%, -0.2%] | 8     |
+| All ❌✅ (primary)                 | 0.0%  | [-0.2%, 0.1%]  | 3     |
+
+* Add arg splat experiment initial tuple impl [#153697](https://github.com/rust-lang/rust/pull/153697) explains the regressions.
+  * New feature, some poking at optimizing perf was attempted and this was
+    best-possible so far. Previous work on this feature improved perf so this
+    series is still a benefit overall in some sense.
+* Improvements from:
+  * Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children [#158360](https://github.com/rust-lang/rust/pull/158360)
+  * perf: Make stable_crate_ids reads lock-free after crate loading [#158185](https://github.com/rust-lang/rust/pull/158185)
+
+Rollup of 15 pull requests [#158508](https://github.com/rust-lang/rust/pull/158508) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=8b95a26baf5820929d86a844317160905e7b325b&end=fd07dbfc91b7b6b3fa76d957e130c51e654131ee&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range          | count |
+|:----------------------------------:|:-----:|:--------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | -     | -              | 0     |
+| Regressions ❌ <br /> (secondary)  | 0.4%  | [0.3%, 0.5%]   | 6     |
+| Improvements ✅ <br /> (primary)   | -0.2% | [-0.3%, -0.2%] | 43    |
+| Improvements ✅ <br /> (secondary) | -0.3% | [-0.4%, -0.2%] | 20    |
+| All ❌✅ (primary)                 | -0.2% | [-0.3%, -0.2%] | 43    |
+
+> The change is the same as [#157996](https://github.com/rust-lang/rust/pull/157996),
+> which was explicitly listed as perf. The overall improvement was deemed to be worth it.
+
+Move `std::io::Error` into `core` [#155625](https://github.com/rust-lang/rust/pull/155625) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=df6ee909ef35c75aa58aa45af6ac071a9b8285c2&end=7fb284d9037fa54f6a9b24261c82b394472cbfd7&stat=instructions:u)
+
+| (instructions:u)                   | mean  | range          | count |
+|:----------------------------------:|:-----:|:--------------:|:-----:|
+| Regressions ❌ <br /> (primary)    | 1.0%  | [0.5%, 2.6%]   | 9     |
+| Regressions ❌ <br /> (secondary)  | 1.4%  | [0.2%, 7.7%]   | 23    |
+| Improvements ✅ <br /> (primary)   | -     | -              | 0     |
+| Improvements ✅ <br /> (secondary) | -4.7% | [-6.0%, -3.2%] | 6     |
+| All ❌✅ (primary)                 | 1.0%  | [0.5%, 2.6%]   | 9     |
+
+Expected mixed results since this change shuffles a lot of code around between
+crates/impl blocks and as a result likely tweaking how much things are
+inlinable. Most of the results are probably fallout from that rather than rustc
+performance changes in a direct sense. I don't think we need to dig deeper here.