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Nov 25, 2021
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add performance triage report for this week #2636

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add performance triage report for this week
pnkfelix Nov 24, 2021
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Update draft/2021-11-24-this-week-in-rust.md
nellshamrell Nov 25, 2021
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21 changes: 7 additions & 14 deletions draft/2021-11-24-this-week-in-rust.md
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Expand Up @@ -97,25 +97,18 @@ If you are a Rust project owner and are looking for contributors, please submit

### Rust Compiler Performance Triage

A large amount of noise in the comparisons this week, likely due to new
probabilistic query hash verification increasing likelihood of changes in each
benchmark; solutions are being tracked in [rustc-perf#1105].

Otherwise, though, the week largely amounted to a neutral one for performance.
There were some regressions, particularly in doc builds, as a result of the
addition of portable SIMD. These are relatively speaking minor and primarily
impact small crates.
This week, there were a number of cases where the `incr-unchanged` variants of `inflate` went up or down by 5% to 6%; we believe these are instances of increased noise in benchmarks documented on [rustc-perf#1105](https://github.com/rust-lang/rustc-perf/issues/1105). I was tempted to remove these from the report, but its non-trivial to re-construct the report "as if" some benchmark were omitted.

[rustc-perf#1105]: https://github.com/rust-lang/rustc-perf/issues/1105
Otherwise, there were some nice wins for performance. For example, PR [#90996](https://github.com/rust-lang/rust/issues/90996) more than halved the time to document builds of `diesel` by revising how we hash `ObligationCauseData`. If anyone is interested, it might be good to follow-up on the effects of PR [#90352](https://github.com/rust-lang/rust/issues/90352), "Simplify `for` loop desugar", where we have hypothesized that the increased compilation time is due to more LLVM optimizations being applied.

Triage done by **@simulacrum**.
Revision range: [eee8b9c7..934624f](https://perf.rust-lang.org/?start=eee8b9c7bafade55981d155dae71657f1cc55a22&end=934624fe5f66ce3fb8abf0597a6deb079783335f&absolute=false&stat=instructions%3Au)
Triage done by **@pnkfelix**.
Revision range: [934624fe..22c2d9dd](https://perf.rust-lang.org/?start=934624fe5f66ce3fb8abf0597a6deb079783335f&end=22c2d9ddbf356bcdb718e88ca6ee3665e1e42690&absolute=false&stat=instructions%3Au)

5 Regressions, 2 Improvements, 6 Mixed; 2 of them in rollups
1 Regressions, 3 Improvements, 8 Mixed; 3 of them in rollups
34 comparisons made in total

41 comparisons made in total

[Full report here](https://github.com/rust-lang/rustc-perf/blob/master/triage/2021-11-16.md)
[Full report here](https://github.com/rust-lang/rustc-perf/blob/master/triage/2021-11-23.md)

### Approved RFCs

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