| # 2023-10-03 Triage Log |
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| A week completely free of pure regressions! The compiler has definitely come out of this week a decent amount faster and less memory hungry than before with the large gain coming from building the compiler with a single CGU on x64 Linux. This not only allows LLVM to do more optimizations across the entire compiler, but should hopefully also result in less non-deterministic performance regressions in the future. This improvement largely comes only at the expense of a few more minutes spent when bootstrapping the compiler. |
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| Triage done by **@rylev**. |
| Revision range: [27b4eb..9998f4](https://perf.rust-lang.org/?start=27b4eb96d13106332d511be2ea6d0c008a57aa6e&end=9998f4add08c3d09c82e00975cf3a293b30160ec&absolute=false&stat=instructions%3Au) |
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| **Summary**: |
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| | (instructions:u) | mean | range | count | |
| |:----------------------------------:|:-----:|:--------------:|:-----:| |
| | Regressions ❌ <br /> (primary) | 1.0% | [0.3%, 6.1%] | 41 | |
| | Regressions ❌ <br /> (secondary) | 2.0% | [0.9%, 7.8%] | 21 | |
| | Improvements ✅ <br /> (primary) | -1.3% | [-5.1%, -0.2%] | 134 | |
| | Improvements ✅ <br /> (secondary) | -1.8% | [-6.9%, -0.2%] | 175 | |
| | All ❌✅ (primary) | -0.8% | [-5.1%, 6.1%] | 175 | |
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| 0 Regressions, 2 Improvements, 4 Mixed; 0 of them in rollups |
| 74 artifact comparisons made in total |
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| #### Regressions |
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| #### Improvements |
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| rustdoc: speed up processing of cross-crate fns to fix a perf regression [#116195](https://github.com/rust-lang/rust/pull/116195) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=177091258c039398d30137b52e1c575a98aa7597&end=5282e5e120128ba589728ee4bcb4f18511ba9fb0&stat=instructions:u) |
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| | (instructions:u) | mean | range | count | |
| |:----------------------------------:|:-----:|:--------------:|:-----:| |
| | Regressions ❌ <br /> (primary) | - | - | 0 | |
| | Regressions ❌ <br /> (secondary) | - | - | 0 | |
| | Improvements ✅ <br /> (primary) | -0.3% | [-0.5%, -0.2%] | 6 | |
| | Improvements ✅ <br /> (secondary) | -0.6% | [-0.8%, -0.3%] | 11 | |
| | All ❌✅ (primary) | -0.3% | [-0.5%, -0.2%] | 6 | |
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| Cleanup number handling in match exhaustiveness [#116281](https://github.com/rust-lang/rust/pull/116281) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=51ddc7467978e265d2004d58980580293734ca93&end=e0d7ed1f453fb54578cc96dfea859b0e7be15016&stat=instructions:u) |
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| | (instructions:u) | mean | range | count | |
| |:----------------------------------:|:-----:|:--------------:|:-----:| |
| | Regressions ❌ <br /> (primary) | - | - | 0 | |
| | Regressions ❌ <br /> (secondary) | - | - | 0 | |
| | Improvements ✅ <br /> (primary) | -0.7% | [-1.5%, -0.3%] | 3 | |
| | Improvements ✅ <br /> (secondary) | - | - | 0 | |
| | All ❌✅ (primary) | -0.7% | [-1.5%, -0.3%] | 3 | |
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| #### Mixed |
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| Don't use a thread to load the dep graph [#116109](https://github.com/rust-lang/rust/pull/116109) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=d23062b5be6bbf5be15226c7f497c89cf7d3d6e1&end=8bf0dec101dc458a411401a826994006abd2f022&stat=instructions:u) |
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| | (instructions:u) | mean | range | count | |
| |:----------------------------------:|:-----:|:--------------:|:-----:| |
| | Regressions ❌ <br /> (primary) | 0.8% | [0.5%, 1.1%] | 2 | |
| | Regressions ❌ <br /> (secondary) | 0.5% | [0.1%, 1.2%] | 3 | |
| | Improvements ✅ <br /> (primary) | -0.2% | [-0.3%, -0.2%] | 4 | |
| | Improvements ✅ <br /> (secondary) | - | - | 0 | |
| | All ❌✅ (primary) | 0.1% | [-0.3%, 1.1%] | 6 | |
| - A very small regression that basically results in net zero change to performance. |
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| Build `rustc` with a single CGU on x64 Linux [#115554](https://github.com/rust-lang/rust/pull/115554) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=c16823d757b376f90c5f5cbd542ce83235befbc4&end=871407a0341262d2a86703ca43b449d35fa5f236&stat=instructions:u) |
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| | (instructions:u) | mean | range | count | |
| |:----------------------------------:|:-----:|:--------------:|:-----:| |
| | Regressions ❌ <br /> (primary) | 0.8% | [0.3%, 2.6%] | 39 | |
| | Regressions ❌ <br /> (secondary) | 1.6% | [0.7%, 2.5%] | 23 | |
| | Improvements ✅ <br /> (primary) | -1.2% | [-3.9%, -0.2%] | 89 | |
| | Improvements ✅ <br /> (secondary) | -1.6% | [-3.5%, -0.4%] | 124 | |
| | All ❌✅ (primary) | -0.6% | [-3.9%, 2.6%] | 128 | |
| - The change is overwhelmingly positive (especially when taking other measures like max RSS and artifact size) making the small regressions acceptable |
| - Take a [look at cycles](https://perf.rust-lang.org/compare.html?start=c16823d757b376f90c5f5cbd542ce83235befbc4&end=871407a0341262d2a86703ca43b449d35fa5f236&stat=cycles%3Au) for a nearly completely regression free view of the positive nature of this change. |
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| Rebased: Mark drop calls in landing pads cold instead of noinline [#102099](https://github.com/rust-lang/rust/pull/102099) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=5333b878c8bc1c4267a67ea3682663629e47541a&end=2e5a9dd6c9eaa42f0684b4b760bd68fc27cbe51b&stat=instructions:u) |
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| | (instructions:u) | mean | range | count | |
| |:----------------------------------:|:-----:|:--------------:|:-----:| |
| | Regressions ❌ <br /> (primary) | 1.5% | [0.3%, 5.9%] | 12 | |
| | Regressions ❌ <br /> (secondary) | 2.7% | [0.4%, 7.7%] | 5 | |
| | Improvements ✅ <br /> (primary) | -0.5% | [-4.5%, -0.2%] | 78 | |
| | Improvements ✅ <br /> (secondary) | -0.9% | [-6.9%, -0.1%] | 65 | |
| | All ❌✅ (primary) | -0.2% | [-4.5%, 5.9%] | 90 | |
| - Largely positive with a few large regressions caused by more time spent in LLVM. This seems to be expected and acceptable. |
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| Make subtyping explicit in MIR [#115025](https://github.com/rust-lang/rust/pull/115025) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=9998f4add08c3d09c82e00975cf3a293b30160ec&end=eb0f3ed59c6508a37c6598bc9762987f053993a7&stat=instructions:u) |
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| | (instructions:u) | mean | range | count | |
| |:----------------------------------:|:-----:|:--------------:|:-----:| |
| | Regressions ❌ <br /> (primary) | 0.6% | [0.4%, 0.8%] | 2 | |
| | Regressions ❌ <br /> (secondary) | 0.5% | [0.1%, 1.1%] | 17 | |
| | Improvements ✅ <br /> (primary) | -0.5% | [-0.6%, -0.5%] | 2 | |
| | Improvements ✅ <br /> (secondary) | -0.5% | [-0.5%, -0.5%] | 1 | |
| | All ❌✅ (primary) | 0.0% | [-0.6%, 0.8%] | 4 | |
| - Small regression that is basically only seen in some secondary benchmarks. Unlikely to be worth deep investigation. |
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