Add triage for 2022-08-16

triage/2022-08-16.md

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+# 2022-08-16 Triage Log
+
+A fairly quiet week for performance, with the exception of the LLVM 15 upgrade
+which resulted in many changes, mostly to the positive.
+
+Triage done by **@simulacrum**.
+Revision range: [cc4dd6fc9f1a5c798df269933c7e442b79661a86..14a459bf37bc19476d43e0045d078121c12d3fef](https://perf.rust-lang.org/?start=cc4dd6fc9f1a5c798df269933c7e442b79661a86&end=14a459bf37bc19476d43e0045d078121c12d3fef&absolute=false&stat=instructions%3Au)
+
+**Summary**:
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.7% | 7.7% | 62    |
+| Regressions ❌ <br /> (secondary) | 1.3% | 5.0% | 51    |
+| Improvements ✅ <br /> (primary) | -1.8% | -6.9% | 93    |
+| Improvements ✅ <br /> (secondary) | -2.4% | -22.0% | 128   |
+| All ❌✅ (primary) | -0.8% | 7.7% | 155   |
+
+
+2 Regressions, 4 Improvements, 2 Mixed; 1 of them in rollups
+38 artifact comparisons made in total
+
+#### Regressions
+
+consider unnormalized types for implied bounds [#99217](https://github.com/rust-lang/rust/pull/99217) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=6d3f1beae1720055e5a30f4dbe7a9e7fb810c65e&end=63e4312e6bd50ec9859c363402209809fb8155d5&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.7% | 1.9% | 37    |
+| Regressions ❌ <br /> (secondary) | 2.0% | 2.4% | 11    |
+| Improvements ✅ <br /> (primary) | -    | -   | 0     |
+| Improvements ✅ <br /> (secondary) | -    | -   | 0     |
+| All ❌✅ (primary) | 0.7% | 1.9% | 37    |
+
+This regression is caused by a soundness fix.
+[#99725](https://github.com/rust-lang/rust/pull/99725) recovered a small amount
+of the lost performance here.
+
+rustdoc: Merge source code pages HTML elements together [#100429](https://github.com/rust-lang/rust/pull/100429) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=4c5665583815a0f0f3e22516441efb43ea6dede2&end=801821d1560f84e4716fcbd9244ec959320a13d5&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.6% | 1.4% | 12    |
+| Regressions ❌ <br /> (secondary) | 1.8% | 3.1% | 8     |
+| Improvements ✅ <br /> (primary) | -    | -   | 0     |
+| Improvements ✅ <br /> (secondary) | -    | -   | 0     |
+| All ❌✅ (primary) | 0.6% | 1.4% | 12    |
+
+The regressions are limited to doc benchmarks and the underlying change reduces
+the number of DOM elements generated by ~30% across a few samples (see PR
+description for details). Those sizes aren't measured by perf.rust-lang.org
+today, so there's no reflection of that here, but the size improvement is a
+welcome one.
+
+#### Improvements
+
+Reoptimize layout array [#99174](https://github.com/rust-lang/rust/pull/99174) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=29e4a9ee0253cd39e552a77f51f11f9a5f1c41e6&end=908fc5b26d15fc96d630ab921e70b2db77a532c4&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -   | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -   | 0     |
+| Improvements ✅ <br /> (primary) | -0.4% | -0.8% | 10    |
+| Improvements ✅ <br /> (secondary) | -0.8% | -1.2% | 5     |
+| All ❌✅ (primary) | -0.4% | -0.8% | 10    |
+
+
+Remove manual implementations of HashStable for hir::Expr and hir::Ty. [#100237](https://github.com/rust-lang/rust/pull/100237) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=3694b7d307b7516757651952b30bb97b6ba5c049&end=ef9810a3e2a9a16e79176cb0d3466ea82d239942&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -   | 0     |
+| Regressions ❌ <br /> (secondary) | -    | -   | 0     |
+| Improvements ✅ <br /> (primary) | -0.2% | -0.2% | 3     |
+| Improvements ✅ <br /> (secondary) | -    | -   | 0     |
+| All ❌✅ (primary) | -0.2% | -0.2% | 3     |
+
+Possibly spurious, but leaving in the report -- bitmaps-3.1.0 check typically does not [see] this much impact on a run to run basis so it's probably at least partially real.
+
+[see]: https://perf.rust-lang.org/index.html?start=2022-07-01&end=ef9810a3e2a9a16e79176cb0d3466ea82d239942&benchmark=bitmaps-3.1.0&profile=check&scenario=incr-unchanged&stat=instructions:u&kind=percentfromfirst
+
+
+Shrink `ast::Attribute`. [#100441](https://github.com/rust-lang/rust/pull/100441) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=8556e6620e4866526b3cea767ad8c20ae877a569&end=14a459bf37bc19476d43e0045d078121c12d3fef&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.6% | 0.6% | 1     |
+| Regressions ❌ <br /> (secondary) | 0.2% | 0.2% | 1     |
+| Improvements ✅ <br /> (primary) | -0.6% | -1.4% | 22    |
+| Improvements ✅ <br /> (secondary) | -1.0% | -1.5% | 23    |
+| All ❌✅ (primary) | -0.5% | -1.4% | 23    |
+
+Mostly an improvement in doc benchmarks, though a few check benchmarks improved
+as well. An excellent win for memory usage, with up to 5.8% wins on helloworld.
+
+passes: load `defined_lib_features` query less [#100328](https://github.com/rust-lang/rust/pull/100328) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=569788e47ee3595c9c6f0e332844d982b3e991c2&end=0068b8bf4b150b506ef0871be4e8652fd4308f84&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | -    | -   | 0     |
+| Regressions ❌ <br /> (secondary) | 0.8% | 1.5% | 3     |
+| Improvements ✅ <br /> (primary) | -0.4% | -0.4% | 1     |
+| Improvements ✅ <br /> (secondary) | -1.2% | -1.8% | 8     |
+| All ❌✅ (primary) | -0.4% | -0.4% | 1     |
+
+The regressions here appear to be spurious, with performance recovering on the
+next commit. Otherwise, this is a good improvement.
+
+#### Mixed
+
+Rollup of 13 pull requests [#100426](https://github.com/rust-lang/rust/pull/100426) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=20ffea6938b5839c390252e07940b99e3b6a889a&end=2ed0f29168f5bc116e747152be600519b5d78bfd&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.3% | 0.4% | 4     |
+| Regressions ❌ <br /> (secondary) | 0.5% | 0.7% | 5     |
+| Improvements ✅ <br /> (primary) | -0.9% | -0.9% | 1     |
+| Improvements ✅ <br /> (secondary) | -1.8% | -1.8% | 1     |
+| All ❌✅ (primary) | 0.0% | -0.9% | 5     |
+
+Small-ish regression narrowed down to
+[#99337](https://github.com/rust-lang/rust/pull/99337), some active work in
+this area of rustdoc is likely to help here soon.
+
+Update to LLVM 15 [#99464](https://github.com/rust-lang/rust/pull/99464) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=b998821e4c51c44a9ebee395c91323c374236bbb&end=e2b52ff73edc8b0b7c74bc28760d618187731fe8&stat=instructions:u)
+
+| (instructions:u) | mean | max | count |
+|:----------------:|:----:|:---:|:-----:|
+| Regressions ❌ <br /> (primary) | 0.8% | 7.5% | 40    |
+| Regressions ❌ <br /> (secondary) | 1.2% | 4.4% | 29    |
+| Improvements ✅ <br /> (primary) | -1.5% | -6.0% | 100   |
+| Improvements ✅ <br /> (secondary) | -2.6% | -21.6% | 94    |
+| All ❌✅ (primary) | -0.9% | 7.5% | 140   |
+
+Overall the benefits here outweigh the negatives, with a number of good
+improvements. LLVM upgrades are something we're going to keep rolling forward
+on regardless. For wall time metrics the improvement here looks particularly
+nice, with bootstrap times improved by ~4%, shaving 30 seconds of the total
+time measured by perf.
+