Remove the `TypedArena::alloc_from_iter` specialization. #116370

nnethercote · 2023-10-03T02:38:25Z

It was added in #78569. It's complicated and doesn't actually help
performance.

r? @cjgillot

rustbot · 2023-10-03T02:38:29Z

Some changes occurred in rustc_ty_utils::consts.rs

cc @BoxyUwU

nnethercote · 2023-10-03T02:38:35Z

@bors try @rust-timer queue

bors · 2023-10-03T02:39:44Z

⌛ Trying commit 2e5e49f with merge 39fc71a...

More arena stuff r? `@ghost`

bors · 2023-10-03T03:53:05Z

☀️ Try build successful - checks-actions
Build commit: 39fc71a (39fc71ad3375354924cb77fd2b30ff0757a0b8f8)

rust-timer · 2023-10-03T05:14:27Z

Finished benchmarking commit (39fc71a): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

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

Instruction count

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

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.3%	[-1.7%, -1.0%]	4
Improvements ✅ (secondary)	-3.4%	[-3.4%, -3.4%]	1
All ❌✅ (primary)	-1.3%	[-1.7%, -1.0%]	4

Cycles

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

Binary size

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

Bootstrap: 624.341s -> 623.869s (-0.08%)
Artifact size: 271.92 MiB -> 271.97 MiB (0.02%)

It was added in rust-lang#78569. It's complicated and doesn't actually help performance. Also, add a comment explaining why the two `alloc_from_iter` functions are so different.

There's no need to collect an iterator into a `Vec`, or to call `into_iter` at the call sites.

nnethercote · 2023-10-03T07:18:23Z

Perf is unchanged, I think this is good to go.

r? @cjgillot

cjgillot · 2023-10-04T11:51:49Z

compiler/rustc_arena/src/lib.rs

+        // Instead we use an approach where any iterator panic will occur
+        // before the memory is allocated. This function is much less hot than
+        // `DroplessArena::alloc_from_iter`, so it doesn't need to be
+        // hyper-optimized.


Do we need a fast path if !needs_drop::<T>()? That would call the drop-less codepath and eventually benefit from the opt.

Not sure I understand the question. Any T not implementing Drop will be allocated in the DroplessArena, as per this comment.

cjgillot · 2023-10-04T20:59:41Z

@bors r+

bors · 2023-10-04T20:59:43Z

📌 Commit a2051dd has been approved by cjgillot

It is now in the queue for this repository.

bors · 2023-10-04T22:32:49Z

⌛ Testing commit a2051dd with merge afe67fa...

bors · 2023-10-05T00:21:36Z

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing afe67fa to master...

rust-timer · 2023-10-05T02:55:57Z

Finished benchmarking commit (afe67fa): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

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

Cycles

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

Binary size

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

Bootstrap: 623.37s -> 622.444s (-0.15%)
Artifact size: 272.00 MiB -> 272.02 MiB (0.01%)

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 3, 2023

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 3, 2023

bors added a commit to rust-lang-ci/rust that referenced this pull request Oct 3, 2023

Auto merge of rust-lang#116370 - nnethercote:more-arena-stuff, r=<try>

39fc71a

More arena stuff r? `@ghost`

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 3, 2023

nnethercote added 2 commits October 3, 2023 18:12

Remove the TypedArena::alloc_from_iter specialization.

816383c

It was added in rust-lang#78569. It's complicated and doesn't actually help performance. Also, add a comment explaining why the two `alloc_from_iter` functions are so different.

Optimize some alloc_from_iter call sites.

a2051dd

There's no need to collect an iterator into a `Vec`, or to call `into_iter` at the call sites.

nnethercote changed the title ~~More arena stuff~~ Remove the TypedArena::alloc_from_iter specialization. Oct 3, 2023

rustbot assigned cjgillot Oct 3, 2023

nnethercote force-pushed the more-arena-stuff branch from 2e5e49f to a2051dd Compare October 3, 2023 07:18

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nnethercote mentioned this pull request Oct 3, 2023

Make TypedArena::alloc_from_iter like DroplessArena::alloc_from_iter. #116327

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cjgillot reviewed Oct 4, 2023

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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 4, 2023

bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 5, 2023

bors merged commit afe67fa into rust-lang:master Oct 5, 2023
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rustbot added this to the 1.75.0 milestone Oct 5, 2023

nnethercote deleted the more-arena-stuff branch October 5, 2023 01:11

pvdrz mentioned this pull request Oct 6, 2023

Fix divergence from upstream master ferrocene/ferrocene#23

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Remove the `TypedArena::alloc_from_iter` specialization. #116370

Remove the `TypedArena::alloc_from_iter` specialization. #116370

nnethercote commented Oct 3, 2023 •

edited

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rust-timer commented Oct 5, 2023

Remove the TypedArena::alloc_from_iter specialization. #116370

Remove the TypedArena::alloc_from_iter specialization. #116370

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nnethercote commented Oct 3, 2023 • edited

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Overall result: no relevant changes - no action needed

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cjgillot commented Oct 4, 2023

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bors commented Oct 5, 2023

rust-timer commented Oct 5, 2023

Overall result: no relevant changes - no action needed

Remove the `TypedArena::alloc_from_iter` specialization. #116370

Remove the `TypedArena::alloc_from_iter` specialization. #116370

nnethercote commented Oct 3, 2023 •

edited