Tweak `VecCache` to improve performance #138405

Zoxc · 2025-03-12T13:49:48Z

This has some tweaks to VecCache to improve performance.

It saves a compare_exchange in complete using the new put_unique function.
It removes bound checks on entries. These are instead checked in the slot_index_exhaustive test.
initialize_bucket is outlined and tuned for that.

rustbot · 2025-03-12T13:49:53Z

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Kobzol · 2025-03-12T14:40:26Z

@bors try @rust-timer queue

bors · 2025-03-12T14:41:37Z

⌛ Trying commit 00e7039 with merge 0b0612c...

Tweak `VecCache` to improve performance This has some tweaks to `VecCache` to improve performance. - It saves a `compare_exchange` in `complete` using the new `put_unique` function. - It removes bound checks on entries. These are instead checked in the `slot_index_exhaustive` test. - `initialize_bucket` is outlined and tuned for that. cc `@Mark-Simulacrum`

bors · 2025-03-12T16:45:51Z

☀️ Try build successful - checks-actions
Build commit: 0b0612c (0b0612c92faadc7268901ca7f18b6859d25f4eba)

Mark-Simulacrum · 2025-03-12T16:55:07Z

compiler/rustc_data_structures/src/vec_cache.rs

    }

    #[cold]
-    fn initialize_bucket<V>(&self, bucket: &AtomicPtr<Slot<V>>) -> *mut Slot<V> {
+    #[inline(never)]
+    fn initialize_bucket<V>(bucket: &AtomicPtr<Slot<V>>, bucket_idx: usize) -> *mut Slot<V> {


Why this change?

It avoids Self needing it exist when not inlined, as the needed information can be passed in registers instead.

rust-timer · 2025-03-12T18:02:35Z

Finished benchmarking commit (0b0612c): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	-	-	0
Regressions ❌ (secondary)	0.9%	[0.2%, 1.8%]	15
Improvements ✅ (primary)	-0.4%	[-0.9%, -0.2%]	140
Improvements ✅ (secondary)	-0.6%	[-1.2%, -0.2%]	42
All ❌✅ (primary)	-0.4%	[-0.9%, -0.2%]	140

Max RSS (memory usage)

Results (primary -2.0%)

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.0%	[-2.8%, -1.2%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.0%	[-2.8%, -1.2%]	2

Cycles

Results (primary 4.1%, secondary -3.1%)

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)	6.8%	[1.6%, 13.7%]	13
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.7%	[-2.1%, -1.4%]	6
Improvements ✅ (secondary)	-3.1%	[-3.5%, -2.5%]	3
All ❌✅ (primary)	4.1%	[-2.1%, 13.7%]	19

Binary size

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

Bootstrap: 779.667s -> 779.823s (0.02%)
Artifact size: 365.24 MiB -> 365.04 MiB (-0.06%)

Zoxc · 2025-03-12T18:23:19Z

Local results:

Benchmark	Before	After		Before	After		Before	After
Benchmark	Time	Time	%	Physical Memory	Physical Memory	%	Committed Memory	Committed Memory	%
🟣 clap:check	1.4028s	1.3962s	-0.47%	147.60 MiB	147.57 MiB	-0.02%	192.07 MiB	192.06 MiB	-0.01%
🟣 hyper:check	0.2335s	0.2321s	-0.58%	80.01 MiB	79.95 MiB	-0.07%	121.83 MiB	121.83 MiB	-0.01%
🟣 regex:check	0.7944s	0.7918s	-0.33%	108.43 MiB	108.50 MiB	0.07%	146.66 MiB	146.80 MiB	0.09%
🟣 syn:check	1.3258s	1.3183s	-0.57%	141.93 MiB	141.92 MiB	-0.01%	180.31 MiB	180.36 MiB	0.03%
Total	3.7565s	3.7385s	-0.48%	477.97 MiB	477.95 MiB	-0.00%	640.87 MiB	641.04 MiB	0.03%
Summary	1.0000s	0.9951s	-0.49%	1 byte	1.00 bytes	-0.01%	1 byte	1.00 bytes	0.03%

Looks like something might be up with html5ever.

Zoxc · 2025-03-12T18:43:07Z

I can't reproduce the html5ever regression locally:

Benchmark	Before	After		Before	After		Before	After
Benchmark	Time	Time	%	Physical Memory	Physical Memory	%	Committed Memory	Committed Memory	%
🟣 html5ever:check	0.6299s	0.6256s	-0.67%	104.10 MiB	103.98 MiB	-0.11%	147.54 MiB	147.58 MiB	0.02%
Total	0.6299s	0.6256s	-0.67%	104.10 MiB	103.98 MiB	-0.11%	147.54 MiB	147.58 MiB	0.02%
Summary	1.0000s	0.9933s	-0.67%	1 byte	1.00 bytes	-0.11%	1 byte	1.00 bytes	0.02%

Kobzol · 2025-03-12T18:56:26Z

Cycles are noisy, although this was high above the threshold. Let's try again, just in case it was a fluke.

@bors try @rust-timer queue

bors · 2025-03-12T18:57:36Z

⌛ Trying commit 00e7039 with merge d06bb14...

Tweak `VecCache` to improve performance This has some tweaks to `VecCache` to improve performance. - It saves a `compare_exchange` in `complete` using the new `put_unique` function. - It removes bound checks on entries. These are instead checked in the `slot_index_exhaustive` test. - `initialize_bucket` is outlined and tuned for that. cc `@Mark-Simulacrum`

bors · 2025-03-12T20:59:19Z

☀️ Try build successful - checks-actions
Build commit: d06bb14 (d06bb14bb9c4c2e005971e2f02d13bb79af6845e)

rust-timer · 2025-03-13T01:36:34Z

Finished benchmarking commit (d06bb14): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	-	-	0
Regressions ❌ (secondary)	1.3%	[0.6%, 1.8%]	10
Improvements ✅ (primary)	-0.4%	[-0.9%, -0.2%]	143
Improvements ✅ (secondary)	-0.6%	[-1.3%, -0.2%]	43
All ❌✅ (primary)	-0.4%	[-0.9%, -0.2%]	143

Max RSS (memory usage)

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

Cycles

Results (primary -1.5%, secondary -2.1%)

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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.5%	[-1.5%, -1.5%]	1
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-1.5%	[-1.5%, -1.5%]	1

Binary size

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

Bootstrap: 779.458s -> 779.323s (-0.02%)
Artifact size: 365.27 MiB -> 365.05 MiB (-0.06%)

Kobzol · 2025-03-13T06:41:42Z

Looks like it was a fluke after all.

Tweak VecCache to improve performance

00e7039

rustbot assigned Noratrieb Mar 12, 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 Mar 12, 2025

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Mark-Simulacrum reviewed Mar 12, 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 Mar 12, 2025

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Mar 13, 2025

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Tweak `VecCache` to improve performance #138405

Tweak `VecCache` to improve performance #138405

Zoxc commented Mar 12, 2025

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rust-timer commented Mar 13, 2025

Kobzol commented Mar 13, 2025

Tweak VecCache to improve performance #138405

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Tweak VecCache to improve performance #138405

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rust-timer commented Mar 12, 2025

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

Zoxc commented Mar 12, 2025

Zoxc commented Mar 12, 2025

Kobzol commented Mar 12, 2025

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bors commented Mar 12, 2025

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rust-timer commented Mar 13, 2025

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

Kobzol commented Mar 13, 2025

Tweak `VecCache` to improve performance #138405

Tweak `VecCache` to improve performance #138405