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Optimized vec::IntoIter::next_chunk impl - #98553

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Jul 27, 2022
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Optimized vec::IntoIter::next_chunk impl#98553
bors merged 2 commits into
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the8472:next_chunk_opt

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@the8472the8472 commented Jun 26, 2022

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x86_64v1, default
test vec::bench_next_chunk ... bench: 696 ns/iter (+/- 22)
x86_64v1, pr
test vec::bench_next_chunk ... bench: 309 ns/iter (+/- 4)
znver2, default
test vec::bench_next_chunk ... bench: 17,272 ns/iter (+/- 117)
znver2, pr
test vec::bench_next_chunk ... bench: 211 ns/iter (+/- 3)

On znver2 the default impl seems to be slow due to different inlining decisions. It goes through core::array::iter_next_chunk
which has a deep call tree.

@rustbotrustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Jun 26, 2022
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rust-highfive commented Jun 26, 2022

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Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

  • Stabilizing library features
  • Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
  • Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
  • Changing public documentation in ways that create new stability guarantees
  • Changing observable runtime behavior of library APIs

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r? @kennytm

(rust-highfive has picked a reviewer for you, use r? to override)

@rust-highfiverust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 26, 2022
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bors commented Jun 29, 2022

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☔ The latest upstream changes (presumably #98680) made this pull request unmergeable. Please resolve the merge conflicts.

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Mark-Simulacrum
Mark-Simulacrum reviewed Jul 26, 2022
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Comment threadlibrary/alloc/src/vec/into_iter.rs Outdated
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Mark-Simulacrum commented Jul 26, 2022

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r=me

@bors rollup=never in case has unexpected perf effects

@Mark-SimulacrumMark-Simulacrum added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 26, 2022
@the8472
Optimized vec::IntoIter::next_chunk impl
2f9f2e5
```
test vec::bench_next_chunk ... bench: 696 ns/iter (+/- 22)
x86_64v1, pr
test vec::bench_next_chunk ... bench: 309 ns/iter (+/- 4)
znver2, default
test vec::bench_next_chunk ... bench: 17,272 ns/iter (+/- 117)
znver2, pr
test vec::bench_next_chunk ... bench: 211 ns/iter (+/- 3)
```
The znver2 default impl seems to be slow due to inlining decisions. It goes through `core::array::iter_next_chunk`
which has a deeper call tree.
@the8472
add test for vec::IntoIter::next_chunk() impl
4ba7cac
an adaption of the default impl's doctest
@the8472

the8472 commented Jul 26, 2022

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@bors r=Mark-Simulacrum

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bors commented Jul 26, 2022

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📌 Commit 4ba7cac has been approved by Mark-Simulacrum

It is now in the queue for this repository.

@borsbors 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 26, 2022
@the8472the8472 mentioned this pull request Jul 26, 2022
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@bors

bors commented Jul 27, 2022

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⌛ Testing commit 4ba7cac with merge b573e10...

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bors commented Jul 27, 2022

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☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing b573e10 to master...

@borsbors added the merged-by-bors This PR was explicitly merged by bors. label Jul 27, 2022
@bors
bors merged commit b573e10 into rust-lang:masterJul 27, 2022
@rustbotrustbot added this to the 1.64.0 milestone Jul 27, 2022
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rust-timer commented Jul 27, 2022

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Finished benchmarking commit (b573e10): comparison url.

Instruction count

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

Max RSS (memory usage)

Results
  • Primary benchmarks: 😿 relevant regression found
  • Secondary benchmarks: mixed results
mean1maxcount2
Regressions 😿
(primary)		2.1%2.1%1
Regressions 😿
(secondary)		3.1%3.9%2
Improvements 🎉
(primary)		N/AN/A0
Improvements 🎉
(secondary)		-2.6%-3.1%2
All 😿🎉 (primary)2.1%2.1%1

Cycles

Results
  • Primary benchmarks: 🎉 relevant improvement found
  • Secondary benchmarks: mixed results
mean1maxcount2
Regressions 😿
(primary)		N/AN/A0
Regressions 😿
(secondary)		3.7%4.6%2
Improvements 🎉
(primary)		-7.2%-7.2%1
Improvements 🎉
(secondary)		-2.3%-2.3%1
All 😿🎉 (primary)-7.2%-7.2%1

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

  1. the arithmetic mean of the percent change↩↩2

  2. number of relevant changes↩↩2

@the8472the8472 mentioned this pull request Aug 1, 2022
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