rust-lang · Mark-Simulacrum · Sep 27, 2022 · Sep 27, 2022
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+# 2022-09-27 Triage Log
+
+Overall a fairly quiet week in terms of new changes; the majority of the delta
+this week was due to reverting
+[#101620](https://github.com/rust-lang/rust/pull/101620), which was a
+regression noted in last week's report.
+
+Triage done by **@simulacrum**.
+Revision range: [8fd6d03e22fba2930ad377b87299de6a37076074..d9297d22ad9edc2b56f0dd8734c1187a0c88be69](https://perf.rust-lang.org/?start=8fd6d03e22fba2930ad377b87299de6a37076074&end=d9297d22ad9edc2b56f0dd8734c1187a0c88be69&absolute=false&stat=instructions%3Au)
+
+**Summary**:
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | 5.6% | [0.4%, 32.9%] | 32    |
+| Regressions ❌ <br /> (secondary) | 7.4% | [0.7%, 25.3%] | 22    |
+| Improvements ✅ <br /> (primary) | -4.0% | [-13.4%, -0.3%] | 135   |
+| Improvements ✅ <br /> (secondary) | -4.3% | [-19.4%, -0.1%] | 123   |
+| All ❌✅ (primary) | -2.2% | [-13.4%, 32.9%] | 167   |
+
+
+2 Regressions, 7 Improvements, 3 Mixed; 3 of them in rollups
+53 artifact comparisons made in total
+
+#### Regressions
+
+a fn pointer doesn't implement `Fn`/`FnMut`/`FnOnce` if its return type isn't sized [#100096](https://github.com/rust-lang/rust/pull/100096) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=4ecfdfac51b159f68fce608792affb34a70e6f73&end=1de00d1ac5247a02184ef7ad044f6521ade7e0cc&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | 23.0% | [21.3%, 25.2%] | 6     |
+| Improvements ✅ <br /> (primary) | -    | -     | 0     |
+| Improvements ✅ <br /> (secondary) | -    | -     | 0     |
+| All ❌✅ (primary) | -    | -     | 0     |
+
+Perf regression is being investigated by @compiler-errors. No positive fix yet
+though; due to the reported regression
+([#102289](https://github.com/rust-lang/rust/pull/102289)) we are thinking that
+just reverting may be the better option. This is a soundness fix though so the
+perf regression may be OK, but further investigation is warranted.
+
+
+Require `#[const_trait]` on `Trait` for `impl const Trait` [#100982](https://github.com/rust-lang/rust/pull/100982) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=626b02a8f97a9e35a647aa18fcdb67cbcb3b09c8&end=7a8636c843bd24038fe1d1f69b4a8e4b0ea55d4e&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.4% | [0.4%, 0.5%] | 6     |
+| Regressions ❌ <br /> (secondary) | 1.5% | [1.5%, 1.5%] | 1     |
+| Improvements ✅ <br /> (primary) | -    | -     | 0     |
+| Improvements ✅ <br /> (secondary) | -    | -     | 0     |
+| All ❌✅ (primary) | 0.4% | [0.4%, 0.5%] | 6     |
+
+This regression was known prior to merging the PR, but the reviewer concluded
+that the small wall-clock delta wasn't worth further investigation. Left a
+comment asking for a better justification of the regression.
+
+#### Improvements
+
+use partition_point instead of binary_search when looking up source lines [#101999](https://github.com/rust-lang/rust/pull/101999) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=7a8636c843bd24038fe1d1f69b4a8e4b0ea55d4e&end=3e50038a2d4029bd1484af75dbf144c4b0da6c74&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -     | 0     |
+| Improvements ✅ <br /> (primary) | -0.3% | [-0.7%, -0.2%] | 62    |
+| Improvements ✅ <br /> (secondary) | -0.6% | [-1.6%, -0.2%] | 41    |
+| All ❌✅ (primary) | -0.3% | [-0.7%, -0.2%] | 62    |
+
+
+Rollup of 10 pull requests [#102150](https://github.com/rust-lang/rust/pull/102150) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=77e7e88567691068f5fba288618023368882d60b&end=bc4d574ff2ffcfe76db36116cc4f193384065985&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -     | 0     |
+| Improvements ✅ <br /> (primary) | -0.3% | [-0.4%, -0.2%] | 4     |
+| Improvements ✅ <br /> (secondary) | -    | -     | 0     |
+| All ❌✅ (primary) | -0.3% | [-0.4%, -0.2%] | 4     |
+
+
+Use internal iteration in `Iterator` comparison methods [#100845](https://github.com/rust-lang/rust/pull/100845) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=e1c28e0c857280ce829beab16ef6082cd518db98&end=06968954f7e11454d49377629bb57d13253384b9&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -     | 0     |
+| Improvements ✅ <br /> (primary) | -1.1% | [-1.1%, -1.1%] | 1     |
+| Improvements ✅ <br /> (secondary) | -    | -     | 0     |
+| All ❌✅ (primary) | -1.1% | [-1.1%, -1.1%] | 1     |
+
+
+Move DepKindStruct from rustc_middle to rustc_query_system [#101710](https://github.com/rust-lang/rust/pull/101710) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=f5193a9fcc73dc09e41a90c5a2c97fc9acc16032&end=ff40f2ec95923c4d45366e85bcff17d75df68d68&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -     | 0     |
+| Improvements ✅ <br /> (primary) | -0.5% | [-0.9%, -0.2%] | 66    |
+| Improvements ✅ <br /> (secondary) | -0.4% | [-0.7%, -0.2%] | 18    |
+| All ❌✅ (primary) | -0.5% | [-0.9%, -0.2%] | 66    |
+
+
+Rollup of 5 pull requests [#102297](https://github.com/rust-lang/rust/pull/102297) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=fe217c28ffc6955f0927d8e8715d43d727debe5a&end=72f4923979979abb5d6b975353e9b3053d257e60&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -     | 0     |
+| Improvements ✅ <br /> (primary) | -0.7% | [-0.7%, -0.7%] | 1     |
+| Improvements ✅ <br /> (secondary) | -1.3% | [-1.5%, -1.2%] | 6     |
+| All ❌✅ (primary) | -0.7% | [-0.7%, -0.7%] | 1     |
+
+
+Fix lint scoping for let-else. [#102257](https://github.com/rust-lang/rust/pull/102257) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=e1d7dec558d863fb76f98453088b36cb1a926d48&end=1d1f1426604b7d79138cdfbb31f82f7f44756fba&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -     | 0     |
+| Improvements ✅ <br /> (primary) | -0.7% | [-0.7%, -0.7%] | 1     |
+| Improvements ✅ <br /> (secondary) | -1.4% | [-1.6%, -1.2%] | 6     |
+| All ❌✅ (primary) | -0.7% | [-0.7%, -0.7%] | 1     |
+
+
+Improve code example for Option::unwrap_or_default [#102283](https://github.com/rust-lang/rust/pull/102283) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=8b705839cd656d202e920efa8769cbe43a5ee269&end=f3a6fbf2f2e898ca4d788b3e686726fa9770c676&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -     | 0     |
+| Improvements ✅ <br /> (primary) | -0.7% | [-0.7%, -0.7%] | 1     |
+| Improvements ✅ <br /> (secondary) | -1.3% | [-1.6%, -1.2%] | 6     |
+| All ❌✅ (primary) | -0.7% | [-0.7%, -0.7%] | 1     |
+
+
+#### Mixed
+
+Revert perf-regression 101620 [#102064](https://github.com/rust-lang/rust/pull/102064) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=199fe1d169b5aeeca0e527ded26542b7a05ebd79&end=bb5a01617589b5e3ece5a36435fc285bfd13c9a4&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | 5.6% | [0.3%, 33.5%] | 33    |
+| Regressions ❌ <br /> (secondary) | 1.1% | [0.3%, 1.5%] | 11    |
+| Improvements ✅ <br /> (primary) | -3.7% | [-12.3%, -0.3%] | 129   |
+| Improvements ✅ <br /> (secondary) | -4.1% | [-19.0%, -0.2%] | 121   |
+| All ❌✅ (primary) | -1.8% | [-12.3%, 33.5%] | 162   |
+
+This fixes a perf regression from last week and the overall trend is an improvement, so as expected.
+
+Use function pointers instead of macro-unrolled loops in rustc_query_impl [#101785](https://github.com/rust-lang/rust/pull/101785) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=ff40f2ec95923c4d45366e85bcff17d75df68d68&end=3288d3a305ad15cfcdcd9ef72404be6d2a2887b5&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -     | 0     |
+| Regressions ❌ <br /> (secondary) | 1.2% | [1.2%, 1.2%] | 2     |
+| Improvements ✅ <br /> (primary) | -0.4% | [-0.4%, -0.4%] | 1     |
+| Improvements ✅ <br /> (secondary) | -1.1% | [-1.5%, -0.6%] | 9     |
+| All ❌✅ (primary) | -0.4% | [-0.4%, -0.4%] | 1     |
+
+Overall mixed results and generally a slight improvement. The seemingly more
+important goal of reducing bootstrap times isn't really achieved by this PR
+though it may help future iteration on these functions by avoiding some LLVM sensitivity.
+
+Rollup of 5 pull requests [#102324](https://github.com/rust-lang/rust/pull/102324) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=1d1f1426604b7d79138cdfbb31f82f7f44756fba&end=8b705839cd656d202e920efa8769cbe43a5ee269&stat=instructions:u)
+
+| (instructions:u) | mean | range | count |
+|:----------------:|:----:|:-----:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.7% | [0.7%, 0.7%] | 1     |
+| Regressions ❌ <br /> (secondary) | 1.4% | [1.3%, 1.6%] | 6     |
+| Improvements ✅ <br /> (primary) | -0.7% | [-0.9%, -0.6%] | 6     |
+| Improvements ✅ <br /> (secondary) | -    | -     | 0     |
+| All ❌✅ (primary) | -0.5% | [-0.9%, 0.7%] | 7     |
+
+keccak, the primary regression, is within its suspected noise level bar.