privacy: Introduce some caching to type visiting in `DefIdVisitorSkeleton` by petrochenkov · Pull Request #147486 · rust-lang/rust

petrochenkov · 2025-10-08T17:00:27Z

The caching fixes compilation speed issues in special cases like #145741, without introducing too much overhead in general cases.

I tried to cache more, but it caused regressions from the caching overhead, like it can be seen from benchmark runs below.

Inspired by #146128.
Closes#145741.

rustbot · 2025-10-08T17:00:32Z

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petrochenkov · 2025-10-08T17:00:44Z

@bors2 try @rust-timer queue

[PERF] privacy: Visit DefIds once in DefIdVisitorSkeleton

rust-bors · 2025-10-08T19:17:21Z

☀️ Try build successful (CI)
Build commit: 665fb0c (665fb0c6194a924362c4847361764e762a482668, parent: 910617d84d611e9ba508fd57a058c59b8a767697)

rust-timer · 2025-10-08T23:24:31Z

Finished benchmarking commit (665fb0c): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.4%	[0.1%, 1.0%]	141
Regressions ❌ (secondary)	0.4%	[0.1%, 1.0%]	77
Improvements ✅ (primary)	-1.3%	[-2.8%, -0.2%]	20
Improvements ✅ (secondary)	-1.2%	[-1.2%, -1.2%]	1
All ❌✅ (primary)	0.2%	[-2.8%, 1.0%]	161

Max RSS (memory usage)

Results (primary 0.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.6%	[0.8%, 4.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[-2.6%, 4.4%]	3

Cycles

Results (secondary -2.9%)

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)	-2.9%	[-2.9%, -2.9%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 473.206s -> 472.658s (-0.12%)
Artifact size: 388.42 MiB -> 388.39 MiB (-0.01%)

petrochenkov · 2025-10-09T10:31:03Z

Interesting, per-DefId caching is a small regression in majority of cases, but provides larger speedups in some cases.
(From local testing, caching at DefId level doesn't help with #145741.)

I'll test per-Ty and per-TraitRef caching next.

petrochenkov · 2025-10-09T12:55:11Z

@bors2 try @rust-timer queue

[PERF] privacy: Visit DefIds once in DefIdVisitorSkeleton

petrochenkov · 2025-10-09T12:59:07Z

The Ty-caching version helps with #145741, and reduces the compilation time from 35 to 16 seconds on my machine.

rust-bors · 2025-10-09T15:28:34Z

☀️ Try build successful (CI)
Build commit: f8e844a (f8e844a5ff3d4e587399f1873c352cd8bb5ba8fd, parent: acf243778e6c54cb7d54bee4be88e510e4be123e)

rust-timer · 2025-10-09T16:42:39Z

Finished benchmarking commit (f8e844a): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.6%	[0.1%, 1.5%]	148
Regressions ❌ (secondary)	0.8%	[0.1%, 3.1%]	130
Improvements ✅ (primary)	-0.5%	[-0.7%, -0.1%]	10
Improvements ✅ (secondary)	-0.5%	[-0.8%, -0.2%]	7
All ❌✅ (primary)	0.5%	[-0.7%, 1.5%]	158

Max RSS (memory usage)

Results (primary 1.4%)

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

	mean	range	count
Regressions ❌ (primary)	3.8%	[3.8%, 3.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.0%	[-1.0%, -1.0%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.4%	[-1.0%, 3.8%]	2

Cycles

Results (secondary 3.0%)

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)	3.0%	[2.0%, 4.9%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 471.876s -> 472.593s (0.15%)
Artifact size: 388.40 MiB -> 388.36 MiB (-0.01%)

rustbot · 2025-10-22T14:30:36Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

…eton`

petrochenkov · 2025-10-22T14:35:43Z

@rustbot ready

lcnr · 2025-10-23T11:52:30Z

@bors r+

bors · 2025-10-23T11:52:33Z

📌 Commit f9464f8 has been approved by lcnr

It is now in the queue for this repository.

bors · 2025-10-23T14:30:13Z

⌛ Testing commit f9464f8 with merge 6501e64...

bors · 2025-10-23T18:30:51Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 6501e64 to master...

github-actions · 2025-10-23T18:34:36Z

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 11d2046 (parent) -> 6501e64 (this PR)

Test differences

Show 4 test diffs

4 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 6501e64fcb02d22b49d6e59d10a7692ec8095619 --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: 7569.5s -> 13800.0s (82.3%)
dist-aarch64-apple: 6319.1s -> 7480.5s (18.4%)
dist-apple-various: 3595.5s -> 4124.5s (14.7%)
dist-various-1: 4287.2s -> 3727.6s (-13.1%)
dist-x86_64-msvc-alt: 9540.9s -> 8621.8s (-9.6%)
x86_64-mingw-1: 9924.8s -> 9031.0s (-9.0%)
i686-msvc-2: 7654.1s -> 8181.6s (6.9%)
dist-x86_64-apple: 7072.6s -> 7494.8s (6.0%)
x86_64-msvc-ext2: 6166.5s -> 5798.5s (-6.0%)
i686-msvc-1: 10165.4s -> 10733.7s (5.6%)

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 · 2025-10-23T20:07:14Z

Finished benchmarking commit (6501e64): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

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)	0.2%	[0.0%, 0.4%]	17
Regressions ❌ (secondary)	0.7%	[0.1%, 1.2%]	6
Improvements ✅ (primary)	-0.4%	[-0.5%, -0.2%]	7
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[-0.5%, 0.4%]	24

Max RSS (memory usage)

Results (primary -2.5%, secondary -4.4%)

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)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-4.4%	[-4.4%, -4.4%]	1
All ❌✅ (primary)	-2.5%	[-2.5%, -2.5%]	1

Cycles

Results (secondary -1.9%)

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)	-1.9%	[-2.5%, -1.4%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 474.995s -> 476.496s (0.32%)
Artifact size: 390.51 MiB -> 390.49 MiB (-0.01%)

panstromek · 2025-10-27T16:11:36Z

perf triage:

This PR fixes exponential blowup. Small regressions from caching overhead are expected.

@rustbot label: +perf-regression-triaged

@petrochenkov It doesn't seem to have such a positive impact in the current benchmark suite. Do you think we should have a reproducer for the original issue in secondary benchmarks, because somebody could accidentaly remove this fix?

petrochenkov · 2025-10-27T16:16:17Z

Do you think we should have a reproducer for the original issue in secondary benchmarks, because somebody could accidentaly remove this fix?

#146128 (comment)

privacy: Introduce some caching to type visiting in `DefIdVisitorSkeleton` The caching fixes compilation speed issues in special cases like rust-lang#145741, without introducing too much overhead in general cases. I tried to cache more, but it caused regressions from the caching overhead, like it can be seen from benchmark runs below. Inspired by rust-lang#146128. Closesrust-lang#145741.

rustbot assigned lcnr Oct 8, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 8, 2025

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rust-borsBot added a commit that referenced this pull request Oct 8, 2025
Auto merge of#147486- petrochenkov:optpriv, r=<try>
665fb0c
[PERF] privacy: Visit DefIds once in DefIdVisitorSkeleton

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 8, 2025

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petrochenkov mentioned this pull request Oct 8, 2025
privacy: cache for trait ref in projection #146128
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petrochenkov force-pushed the optpriv branch from e82b9dc to 440e11eCompare October 9, 2025 12:54

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rust-borsBot added a commit that referenced this pull request Oct 9, 2025
Auto merge of#147486- petrochenkov:optpriv, r=<try>
f8e844a
[PERF] privacy: Visit DefIds once in DefIdVisitorSkeleton

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 9, 2025

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 9, 2025

petrochenkov added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Oct 22, 2025

privacy: Avoid some unnecessary mutability
156499e

petrochenkov force-pushed the optpriv branch from cf1911e to 8d3a7ebCompare October 22, 2025 14:30

privacy: Introduce some caching to type visiting in `DefIdVisitorSkel…
f9464f8
…eton`

petrochenkov force-pushed the optpriv branch from 8d3a7eb to f9464f8Compare October 22, 2025 14:31

petrochenkov changed the title ~~[PERF] privacy: Visit DefIds once in DefIdVisitorSkeleton~~privacy: Introduce some caching to type visiting in DefIdVisitorSkeletonOct 22, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 22, 2025

petrochenkov mentioned this pull request Oct 22, 2025
Exponential slow down in compilation speed (because of visiblity checking?) #145741
Closed

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 Oct 23, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 23, 2025

bors merged commit 6501e64 into rust-lang:masterOct 23, 2025
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rustbot added this to the 1.92.0 milestone Oct 23, 2025

rustbot added the perf-regression-triaged The performance regression has been triaged. label Oct 27, 2025

github-actionsBot mentioned this pull request Oct 30, 2025
Toolchain upgrade to nightly-2026-02-09 flux-rs/flux#1345
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petrochenkov deleted the optpriv branch June 17, 2026 14:54

petrochenkov mentioned this pull request Aug 1, 2026
perf: Cache already-checked types in the privacy visitor #160317
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Overall result: ❌✅ regressions and improvements - please read the text below

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Overall result: ❌✅ regressions and improvements - please read the text below

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Test differences

Job duration changes

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Overall result: ❌✅ regressions and improvements - please read the text below

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