Perf regression fix by Kivooeo · Pull Request #150056 · rust-lang/rust

Kivooeo · 2025-12-16T11:54:17Z

The only thing changed from the previous PR is that I removed output_is_inhabited from hot path, and hide it behind condition, so now it will compute it less frequent

follow up on #149664

Kivooeo · 2025-12-16T17:05:10Z

@rust-timer build 9124eca

Kivooeo · 2025-12-16T17:06:58Z

@Kobzol how do i run this

Kobzol · 2025-12-16T17:13:02Z

@bors try @rust-timer queue

trying to address perf regression

rust-bors · 2025-12-16T19:29:54Z

☀️ Try build successful (CI)
Build commit: 48c5d38 (48c5d3879672c42316e3b17a082885381ab2cfb9, parent: 95a27adcf907bcc1046602c3746dad8cfdf3bf3f)

rust-timer · 2025-12-16T20:11:19Z

Finished benchmarking commit (48c5d38): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.2%]	19
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.2%]	12
All ❌✅ (primary)	-0.2%	[-0.3%, -0.2%]	19

Max RSS (memory usage)

Results (primary 2.1%, secondary 2.2%)

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

	mean	range	count
Regressions ❌ (primary)	2.1%	[2.1%, 2.1%]	1
Regressions ❌ (secondary)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.1%	[2.1%, 2.1%]	1

Cycles

Results (secondary -2.7%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.9%, -2.5%]	2
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 479.485s -> 478.535s (-0.20%)
Artifact size: 390.32 MiB -> 390.28 MiB (-0.01%)

Kivooeo · 2025-12-16T20:14:42Z

hm, wait how do I even understand if perf is fine? is there a way to check perf between two commits? I believe there's been a numerous amount of changes in this period of time that affects a bootstrap time

but on the other hand it's not a 5 second reduce, not sure how to interpret this results

Kobzol · 2025-12-16T20:16:11Z

Bootstrap time is not super important here, I would say. Based on the icount results, it looks like this change does indeed fix the regression!

rustbot · 2025-12-16T20:17:12Z

r? @SparrowLii

rustbot has assigned @SparrowLii.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Kivooeo · 2025-12-16T20:17:26Z

r? @davidtwco

Kivooeo · 2025-12-16T20:19:01Z

Based on the icount results, it looks like this change does indeed fix the regression!

Ah, thanks for the clarification!

Kivooeo · 2025-12-16T21:35:16Z

I want to try different approach, should be even better, do I need to rerun bors try before next perf run?

Kobzol · 2025-12-16T21:36:15Z

Yes, rustc-perf always benchmarks the result of the try build :)

@bors try @rust-timer queue

Perf regression fix

rust-bors · 2025-12-16T23:53:44Z

☀️ Try build successful (CI)
Build commit: da3c48f (da3c48f3bacfa34354f911642899ba5eb24ea620, parent: 31010ca61c3ff019e1480dda0a7ef16bd2bd51c0)

rust-timer · 2025-12-17T00:35:14Z

Finished benchmarking commit (da3c48f): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.2%]	18
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.2%]	10
All ❌✅ (primary)	-0.2%	[-0.3%, -0.2%]	18

Max RSS (memory usage)

Results (primary 2.0%, secondary -0.3%)

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

	mean	range	count
Regressions ❌ (primary)	2.0%	[2.0%, 2.0%]	1
Regressions ❌ (secondary)	4.3%	[4.3%, 4.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.6%	[-3.0%, -2.3%]	2
All ❌✅ (primary)	2.0%	[2.0%, 2.0%]	1

Cycles

Results (secondary 3.1%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.1%	[3.1%, 3.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 479.038s -> 478.549s (-0.10%)
Artifact size: 390.32 MiB -> 390.27 MiB (-0.01%)

Kivooeo · 2025-12-17T00:54:58Z

looks slightly better right?

Kobzol · 2025-12-17T08:03:26Z

Looks pretty much the same to me.

Kivooeo · 2025-12-18T15:41:59Z

Nominate this to beta backport as was discussed on todays triage meeting because it's a follow up on a beta accepted PR

@rustbot label +beta-nominated

davidtwco · 2025-12-19T14:12:20Z

@bors r+

bors · 2025-12-19T14:12:24Z

📌 Commit fc0d01b has been approved by davidtwco

It is now in the queue for this repository.

bors · 2025-12-19T18:18:14Z

⌛ Testing commit fc0d01b with merge 806c2a3...

bors · 2025-12-19T21:30:23Z

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing 806c2a3 to main...

github-actions · 2025-12-19T21:33:11Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing b889870 (parent) -> 806c2a3 (this PR)

Test differences

Show 2 test diffs

2 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 806c2a35dcc1db7867864fea0a7a65554a5238b7 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

aarch64-apple: 11536.2s -> 9361.6s (-18.9%)
pr-check-1: 1913.0s -> 1559.0s (-18.5%)
x86_64-gnu-miri: 4858.9s -> 4149.4s (-14.6%)
x86_64-gnu-tools: 3753.8s -> 3258.4s (-13.2%)
test-various: 7619.6s -> 6635.9s (-12.9%)
x86_64-gnu-llvm-21-3: 7077.5s -> 6224.2s (-12.1%)
i686-gnu-2: 6017.0s -> 5310.1s (-11.7%)
i686-gnu-1: 8459.0s -> 7480.3s (-11.6%)
dist-powerpc64-linux: 5940.8s -> 5281.5s (-11.1%)
dist-x86_64-apple: 7408.8s -> 8153.6s (+10.1%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-12-19T22:11:57Z

Finished benchmarking commit (806c2a3): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.2%]	18
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.1%]	12
All ❌✅ (primary)	-0.2%	[-0.3%, -0.2%]	18

Max RSS (memory usage)

Results (primary -3.5%, secondary 1.6%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.6%	[0.9%, 2.2%]	2
Improvements ✅ (primary)	-3.5%	[-6.5%, -1.5%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.5%	[-6.5%, -1.5%]	3

Cycles

Results (primary 6.7%, 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)	6.7%	[2.2%, 18.8%]	7
Regressions ❌ (secondary)	4.7%	[2.1%, 9.7%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	6.7%	[2.2%, 18.8%]	7

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 479.396s -> 477.964s (-0.30%)
Artifact size: 390.52 MiB -> 390.53 MiB (0.00%)

apiraino · 2026-01-08T15:13:49Z

Beta backport declined as per compiler team on Zulip. The advantages are thin and don't make the backport a compelling choice.

@rustbot label -beta-nominated

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Dec 16, 2025

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rust-bors Bot added a commit that referenced this pull request Dec 16, 2025

Auto merge of #150056 - Kivooeo:trying-to-address-perf, r=<try>

48c5d38

trying to address perf regression

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Kivooeo marked this pull request as ready for review December 16, 2025 20:17

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Dec 16, 2025

rustbot assigned SparrowLii Dec 16, 2025

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Dec 16, 2025

rustbot assigned davidtwco and unassigned SparrowLii Dec 16, 2025

Kivooeo changed the title ~~trying to address perf regression~~ Perf regression fix Dec 16, 2025

make the check calls fewer times

fc0d01b

rust-cloud-vms Bot force-pushed the trying-to-address-perf branch from 9124eca to fc0d01b Compare December 16, 2025 21:34

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rust-bors Bot added a commit that referenced this pull request Dec 16, 2025

Auto merge of #150056 - Kivooeo:trying-to-address-perf, r=<try>

da3c48f

Perf regression fix

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Dec 16, 2025

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Dec 17, 2025

rustbot added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Dec 18, 2025

davidtwco approved these changes Dec 19, 2025

View reviewed changes

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 19, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Dec 19, 2025

bors merged commit 806c2a3 into rust-lang:main Dec 19, 2025
13 checks passed

rustbot added this to the 1.94.0 milestone Dec 19, 2025

Kivooeo mentioned this pull request Dec 20, 2025

[beta] backports #150214

Merged

github-actions Bot mentioned this pull request Dec 23, 2025

Toolchain upgrade to nightly-2026-02-09 flux-rs/flux#1345

Open

rustbot removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Jan 8, 2026

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Overall result: ✅ improvements - no action needed

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Overall result: ✅ improvements - no action needed

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Test differences

Job duration changes

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Overall result: ✅ improvements - no action needed

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