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Reduce optimization level #149428

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@Mark-Simulacrum Mark-Simulacrum commented Nov 28, 2025

Mostly trying to see what the delta in build time vs. runtime performance is on our perf suite, I think it's unlikely we'd want to land this.

r? ghost

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Reduce optimization level
d6e2eb5 
Mostly trying to see what the delta in build time vs. runtime
performance is on our perf suite, I think it's unlikely we'd want to
land this.
@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels Nov 28, 2025
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Mark-Simulacrum commented Nov 28, 2025

@bors try @rust-timer queue

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rust-bors bot added a commit that referenced this pull request Nov 28, 2025
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Auto merge of #149428 - Mark-Simulacrum:opt-level-1, r=<try>
27641ce 
Reduce optimization level
@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Nov 28, 2025
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rust-bors bot commented Nov 28, 2025

☀️ Try build successful (CI)
Build commit: 27641ce (27641cefbed45ce5077076aeee68006ab17894d2, parent: 9050733395f7c10560d49f549e022f411fa28cea)

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rust-timer commented Nov 29, 2025

Finished benchmarking commit (27641ce): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

mean range count
Regressions ❌
(primary)		 14.8% [0.7%, 29.9%] 269
Regressions ❌
(secondary)		 16.8% [0.6%, 52.0%] 314
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 14.8% [0.7%, 29.9%] 269

Max RSS (memory usage)

Results (primary 3.4%, secondary 4.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

mean range count
Regressions ❌
(primary)		 3.4% [0.5%, 11.5%] 131
Regressions ❌
(secondary)		 4.7% [0.6%, 11.9%] 258
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 3.4% [0.5%, 11.5%] 131

Cycles

Results (primary 8.9%, secondary 12.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

mean range count
Regressions ❌
(primary)		 8.9% [2.0%, 24.4%] 244
Regressions ❌
(secondary)		 12.0% [1.6%, 48.9%] 301
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 8.9% [2.0%, 24.4%] 244

Binary size

Results (primary 0.1%, secondary 0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

mean range count
Regressions ❌
(primary)		 0.1% [0.1%, 0.1%] 4
Regressions ❌
(secondary)		 0.1% [0.1%, 0.1%] 34
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 0.1% [0.1%, 0.1%] 4

Bootstrap: 473.019s -> 360.071s (-23.88%)
Artifact size: 386.89 MiB -> 456.05 MiB (17.88%)

@rustbot rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Nov 29, 2025
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