Return an iterator instead of a `Vec` in rustdoc `Item::attributes` #140441

GuillaumeGomez · 2025-04-29T09:31:05Z

Let's see if it has an impact on performance.

r? ghost

GuillaumeGomez · 2025-04-29T09:31:30Z

bors · 2025-04-29T09:32:42Z

⌛ Trying commit b7de7a0 with merge 1b81120...

…ec, r=<try> Return an iterator instead of a `Vec` in rustdoc `Item::attributes` Let's see if it has an impact on performance. r? ghost

bors · 2025-04-29T11:38:33Z

☀️ Try build successful - checks-actions
Build commit: 1b81120 (1b81120a15b63f5d48a4ace1d5be8416031db67c)

rust-timer · 2025-04-29T17:08:06Z

Finished benchmarking commit (1b81120): comparison URL.

Overall result: ❌ regressions - please read the text below

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.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	1.6%	[0.2%, 3.0%]	2
Regressions ❌ (secondary)	0.7%	[0.7%, 0.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.6%	[0.2%, 3.0%]	2

Max RSS (memory usage)

Results (primary -0.7%)

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)	-0.7%	[-0.8%, -0.5%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.7%	[-0.8%, -0.5%]	2

Cycles

Results (primary 1.0%, secondary -5.4%)

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)	1.7%	[0.5%, 2.8%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.5%, -0.5%]	1
Improvements ✅ (secondary)	-5.4%	[-14.6%, -1.6%]	20
All ❌✅ (primary)	1.0%	[-0.5%, 2.8%]	3

Binary size

Results (primary 1.1%)

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)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	1

Bootstrap: 763.658s -> 763.537s (-0.02%)
Artifact size: 365.42 MiB -> 365.22 MiB (-0.06%)

GuillaumeGomez · 2025-04-29T21:22:45Z

Small regression. Gonna try to make it better.

GuillaumeGomez · 2025-05-02T14:17:47Z

@bors try @rust-timer queue

…ec, r=<try> Return an iterator instead of a `Vec` in rustdoc `Item::attributes` Let's see if it has an impact on performance. r? ghost

bors · 2025-05-02T14:18:58Z

⌛ Trying commit 9d14b47 with merge 9efc522...

bors · 2025-05-02T16:24:36Z

☀️ Try build successful - checks-actions
Build commit: 9efc522 (9efc522381d82f77519ec169a2f081e2d99e95fc)

rust-timer · 2025-05-02T18:01:26Z

Finished benchmarking commit (9efc522): 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 (primary -0.4%, secondary 3.5%)

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)	0.7%	[0.4%, 1.7%]	7
Regressions ❌ (secondary)	3.5%	[3.5%, 3.5%]	1
Improvements ✅ (primary)	-1.5%	[-5.7%, -0.4%]	7
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-5.7%, 1.7%]	14

Cycles

Results (primary 0.3%)

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)	0.6%	[0.4%, 1.6%]	16
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-1.4%, -0.4%]	6
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[-1.4%, 1.6%]	22

Binary size

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

Bootstrap: 766.288s -> 768.378s (0.27%)
Artifact size: 365.55 MiB -> 365.45 MiB (-0.03%)

GuillaumeGomez · 2025-05-02T19:19:14Z

I'm surprised the impact is so small for both memory and CPU...

r? @notriddle

If you don't think it's worth keeping, I'll just close the PR.

notriddle · 2025-05-04T01:18:47Z

src/librustdoc/clean/types.rs

+        if self.done {
+            return None;
+        }
+        let ret = self.item.adt_item_extra_attrs(self.tcx, self.document_private);
+        self.done = true;
+        ret


Lees intermediate variables.

Suggested change

if self.done {

return None;

}

let ret = self.item.adt_item_extra_attrs(self.tcx, self.document_private);

self.done = true;

ret

if self.done {

None

} else {

self.done = true;

self.item.adt_item_extra_attrs(self.tcx, self.document_private)

}

notriddle · 2025-05-04T02:09:01Z

src/librustdoc/clean/types.rs

+                    Some(
+                        rustc_hir_pretty::attribute_to_string(&tcx, attr)
+                            .replace("\\\n", "")
+                            .replace('\n', "")
+                            .replace("  ", " "),
+                    )


I wonder if this makes a measurable improvement?

Suggested change

Some(

rustc_hir_pretty::attribute_to_string(&tcx, attr)

.replace("\\\n", "")

.replace('\n', "")

.replace(" ", " "),

)

let attr = rustc_hir_pretty::attribute_to_string(&tcx, attr);

Some(

if attr.contains(['\n', '\\']) || attr.contains(" ") {

attr

.replace("\\\n", "")

.replace('\n', "")

.replace(" ", " ")

} else {

attr

}

)

notriddle · 2025-05-04T02:17:07Z

src/librustdoc/json/conversions.rs

            .collect();
        let docs = item.opt_doc_value();
-        let attrs = item.attributes(self.tcx, self.cache(), true);
+        let attrs = item.attributes(self.tcx, self.cache(), true).collect::<Vec<_>>();


Another potential memory-use improvement.

Suggested change

let attrs = item.attributes(self.tcx, self.cache(), true).collect::<Vec<_>>();

let attrs = item.attributes(self.tcx, self.cache(), true).collect::<ThinVec<_>>();

This requires changing rustdoc-json-types so maybe in a follow-up. Let's see if the rest of your suggestions will work.

GuillaumeGomez · 2025-05-05T12:50:06Z

Let's see if there is an improvement!

@bors try @rust-timer queue

…ec, r=<try> Return an iterator instead of a `Vec` in rustdoc `Item::attributes` Let's see if it has an impact on performance. r? ghost

bors · 2025-05-05T12:51:18Z

⌛ Trying commit 8e07721 with merge d5f9630...

bors · 2025-05-05T15:00:35Z

☀️ Try build successful - checks-actions
Build commit: d5f9630 (d5f963095693d154e91c26822a3fcc6f6de58ee9)

rust-timer · 2025-05-05T18:09:19Z

Finished benchmarking commit (d5f9630): comparison URL.

Overall result: ✅ improvements - 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 is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.5%	[-1.5%, -1.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.5%	[-1.5%, -1.5%]	1

Max RSS (memory usage)

Results (primary 0.6%, secondary 1.0%)

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)	0.8%	[0.4%, 2.1%]	12
Regressions ❌ (secondary)	1.0%	[1.0%, 1.0%]	1
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.5%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.6%	[-0.6%, 2.1%]	14

Cycles

Results (primary 0.3%)

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)	0.6%	[0.4%, 1.1%]	25
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.8%	[-1.3%, -0.5%]	6
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[-1.3%, 1.1%]	31

Binary size

Results (primary -0.4%)

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)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	1

Bootstrap: 768.8s -> 771.846s (0.40%)
Artifact size: 365.42 MiB -> 365.37 MiB (-0.01%)

GuillaumeGomez · 2025-05-05T19:35:24Z

Still no significant impact. I'll let it up to you notriddle whether or not you think this improvement is still worth keeping. 😉

notriddle · 2025-05-05T22:24:11Z

No, I don't think it is. If it were written as a straight-line generator, maybe it would work, but as long as it requires a manual iterator adapter, it's not worth it.

rustbot added A-rustdoc-json Area: Rustdoc JSON backend S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. labels Apr 29, 2025

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Apr 29, 2025

GuillaumeGomez force-pushed the iterator-instead-of-vec branch from b7de7a0 to 9d14b47 Compare May 2, 2025 14:17

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rustbot removed S-waiting-on-perf Status: Waiting on a perf run to be completed. perf-regression Performance regression. labels May 2, 2025

rustbot assigned notriddle May 2, 2025

notriddle reviewed May 4, 2025

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Return an iterator instead of a Vec in rustdoc Item::attributes

8e07721

GuillaumeGomez force-pushed the iterator-instead-of-vec branch from 9d14b47 to 8e07721 Compare May 5, 2025 12:45

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notriddle closed this May 5, 2025

GuillaumeGomez deleted the iterator-instead-of-vec branch May 6, 2025 09:23

	let attrs = item.attributes(self.tcx, self.cache(), true).collect::<Vec<_>>();
	let attrs = item.attributes(self.tcx, self.cache(), true).collect::<ThinVec<_>>();

Return an iterator instead of a Vec in rustdoc Item::attributes #140441

Return an iterator instead of a Vec in rustdoc Item::attributes #140441

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bors commented Apr 29, 2025

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rust-timer commented Apr 29, 2025

Overall result: ❌ regressions - please read the text below

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rust-timer commented May 2, 2025

Overall result: no relevant changes - no action needed

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rust-timer commented May 5, 2025

Overall result: ✅ improvements - no action needed

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Return an iterator instead of a `Vec` in rustdoc `Item::attributes` #140441

Return an iterator instead of a `Vec` in rustdoc `Item::attributes` #140441