Avoid the arena_cache modifier for several queries

[Zalathar]

View all comments

The arena_cache query modifier is convenient, but we can potentially avoid some overhead by allocating values into the central tcx.arena when possible.

There should be no change to compiler output.

[Zalathar]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 6f7d022 (6f7d022409d054eabfd477aad3fabdfbd1d91cbc)
Base parent: 7022271 (70222712809cd5cc1718ed8995914a1cbacb6b92)

[rust-timer]

Finished benchmarking commit (6f7d022): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)	0.3%	[0.3%, 0.3%]	1
Regressions ❌ (secondary)	0.1%	[0.1%, 0.2%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.1%]	5
All ❌✅ (primary)	0.3%	[0.3%, 0.3%]	1

Max RSS (memory usage)

Results (primary -1.3%, secondary 0.2%)

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

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	3.4%	[0.8%, 6.7%]	9
Improvements ✅ (primary)	-1.5%	[-3.4%, -0.7%]	10
Improvements ✅ (secondary)	-2.0%	[-3.2%, -0.8%]	13
All ❌✅ (primary)	-1.3%	[-3.4%, 1.1%]	11

Cycles

Results (primary 2.4%, secondary 7.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.4%	[2.4%, 2.4%]	1
Regressions ❌ (secondary)	7.9%	[2.1%, 13.7%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.4%	[2.4%, 2.4%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 475.539s -> 474.177s (-0.29%)
Artifact size: 400.59 MiB -> 400.51 MiB (-0.02%)

[Zalathar]

Let's try another perf run on the same changes (rebased) to get a sense of whether those micro-regressions are noise or real.

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 010d6dc (010d6dc97ceeb9ca121a70f1e97c204f1cbfc1ed)
Base parent: 5db7f4b (5db7f4be8a36c1b8ae19299469e2be2b0f052c21)

[rust-timer]

Finished benchmarking commit (010d6dc): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)	0.3%	[0.3%, 0.3%]	1
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.2%, -0.1%]	4
All ❌✅ (primary)	0.3%	[0.3%, 0.3%]	1

Max RSS (memory usage)

Results (secondary -0.5%)

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)	3.7%	[0.7%, 6.2%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.8%	[-8.0%, -1.1%]	4
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 3.6%, 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)	3.6%	[2.9%, 4.5%]	6
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	3.6%	[2.9%, 4.5%]	6

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 475.082s -> 471.158s (-0.83%)
Artifact size: 400.59 MiB -> 400.40 MiB (-0.05%)

[Zalathar]

As an experiment, let's try with only the subset of changes that use the dropless arena:

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 54e6c6c (54e6c6c04cc2470c1bc15d68c6b420b505075d4e)
Base parent: edc52f8 (edc52f87c28f328c61685a02c47887a5cec7d767)

[rustbot]

This PR was rebased onto a different main 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.

[Zalathar]

Rebased, and PR CI is green.

@bors r=nnethercote

[rust-bors]

📌 Commit be58a50 has been approved by nnethercote

It is now in the queue for this repository.

[Zalathar]

• The queue is mostly empty and this PR has been waiting for a few days now, so I'm going to put this ahead of Rollup of 2 pull requests #162347 on the assumption that we can make a bigger rollup later.

@bors p=5 (rollup=never ahead of small rollup)

[rust-bors]

☀️ Test successful - CI
Approved by: nnethercote
Duration: 3h 8m 9s
Pushing dbad1ba to main...

[github-actions]

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 f248f40 (parent) -> dbad1ba (this PR)

Test differences

Show 190 test diffs

190 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 dbad1bab60868d49978b716635ac2c3203e327cf --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

1. dist-x86_64-solaris: 1h 3m -> 1h 42m (+61.0%)
2. i686-gnu-nopt-1: 1h 31m -> 2h 26m (+59.9%)
3. i686-gnu-1: 1h 43m -> 2h 23m (+38.2%)
4. x86_64-msvc-2: 1h 50m -> 2h 30m (+36.4%)
5. dist-ohos-aarch64: 1h 22m -> 53m 25s (-35.4%)
6. x86_64-gnu-llvm-21-1: 38m 41s -> 50m 54s (+31.6%)
7. dist-x86_64-freebsd: 1h 33m -> 1h 5m (-30.0%)
8. x86_64-gnu-tools: 56m 1s -> 1h 12m (+29.3%)
9. dist-x86_64-illumos: 1h 54m -> 1h 21m (-28.7%)
10. optional-x86_64-gnu-autodiff: 43m 59s -> 56m 2s (+27.4%)

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]

Finished benchmarking commit (dbad1ba): comparison URL.

Overall result: ❌✅ regressions and 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)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	1

Max RSS (memory usage)

Results (secondary -0.4%)

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)	4.1%	[2.7%, 6.9%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.8%	[-4.4%, -3.2%]	4
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 3.0%, 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)	3.0%	[2.7%, 3.4%]	2
Regressions ❌ (secondary)	3.1%	[3.1%, 3.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.0%	[2.7%, 3.4%]	2

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 476.686s -> 478.423s (0.36%)
Artifact size: 403.40 MiB -> 403.41 MiB (0.00%)