Group dep nodes by chunks with sequential indices and only store the first index at the start of the chunk

[Zoxc]

This groups dep nodes by chunks with sequential indices and only stores the first index at the start of the chunk. This should reduce the dep graph size overhead from #139756.

[rustbot]

r? @nnethercote

rustbot has assigned @nnethercote.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[Zoxc]

@bors try @rust-timer queue

[bors]

⌛ Trying commit d17b845 with merge 4e914b4...

[bors]

☀️ Try build successful - checks-actions
Build commit: 4e914b4 (4e914b460df7796cb8d6706e20af7bb5db733ed6)

[rust-timer]

Finished benchmarking commit (4e914b4): comparison URL.

Overall result: ❌✅ regressions and improvements - BENCHMARK(S) FAILED

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

❗ ❗ ❗ ❗ ❗
Warning ⚠️: The following benchmark(s) failed to build:

• html5ever-0.31.0
• hyper-0.14.18
• cargo-0.87.1

❗ ❗ ❗ ❗ ❗

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)	0.3%	[0.3%, 0.4%]	2
Regressions ❌ (secondary)	0.4%	[0.4%, 0.4%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-1.3%, -0.2%]	20
All ❌✅ (primary)	0.3%	[0.3%, 0.4%]	2

Max RSS (memory usage)

Results (primary -0.2%, secondary 2.8%)

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)	0.9%	[0.4%, 1.3%]	3
Regressions ❌ (secondary)	3.5%	[2.0%, 5.0%]	7
Improvements ✅ (primary)	-1.9%	[-3.2%, -0.6%]	2
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-0.2%	[-3.2%, 1.3%]	5

Cycles

Results (primary 0.8%)

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%, 1.5%]	6
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.8%	[0.4%, 1.5%]	6

Binary size

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

Bootstrap: 775.41s -> 777.006s (0.21%)
Artifact size: 365.09 MiB -> 365.18 MiB (0.03%)

[nnethercote]

This is marked as a draft so I will...

@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[bors]

☔ The latest upstream changes (presumably #121909) made this pull request unmergeable. Please resolve the merge conflicts.

[Zoxc]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 5825e91 (5825e9148310a7b5ee29a006265dcba5e4cdc5de, parent: f60a0f1bcc5a2a6dd8eb2d2021da79b40f5fbae9)

[rust-timer]

Finished benchmarking commit (5825e91): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@bors rollup=never
@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%	[0.2%, 0.5%]	38
Regressions ❌ (secondary)	0.3%	[0.2%, 0.4%]	25
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.2%, 0.5%]	38

Max RSS (memory usage)

Results (primary 0.1%, secondary 1.8%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	1.8%	[1.8%, 1.8%]	1
Improvements ✅ (primary)	-1.0%	[-1.2%, -0.8%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[-1.2%, 2.2%]	3

Cycles

Results (primary 3.6%, secondary 1.8%)

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

	mean	range	count
Regressions ❌ (primary)	3.6%	[3.4%, 3.9%]	2
Regressions ❌ (secondary)	3.1%	[2.1%, 5.5%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.1%	[-5.4%, -4.8%]	2
All ❌✅ (primary)	3.6%	[3.4%, 3.9%]	2

Binary size

Results (primary 0.0%, secondary 0.1%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	10
Regressions ❌ (secondary)	0.1%	[0.0%, 0.1%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	10

Bootstrap: 470.454s -> 473.967s (0.75%)
Artifact size: 397.65 MiB -> 397.71 MiB (0.01%)

[Zoxc]

The expected dep graph reductions show up on perf, but I don't see why instructions would slightly regress, as we're now decoding / encoding less. Locally it's a slight improvement:

Benchmark	Before	After		Before	After		Before	After
	Time	Time	%	Physical Memory	Physical Memory	%	Committed Memory	Committed Memory	%
🟣 clap:check:unchanged	0.2488s	0.2466s	-0.87%	98.63 MiB	98.27 MiB	-0.36%	164.04 MiB	163.62 MiB	-0.25%
🟣 hyper:check:unchanged	0.1086s	0.1084s	-0.22%	62.72 MiB	62.71 MiB	-0.02%	120.30 MiB	120.31 MiB	0.01%
🟣 regex:check:unchanged	0.1837s	0.1835s	-0.08%	80.15 MiB	80.58 MiB	0.55%	141.44 MiB	141.84 MiB	0.29%
🟣 syn:check:unchanged	0.4024s	0.3997s	-0.68%	119.71 MiB	119.88 MiB	0.14%	185.17 MiB	185.39 MiB	0.12%
Total	0.9435s	0.9382s	-0.56%	361.20 MiB	361.45 MiB	0.07%	610.94 MiB	611.17 MiB	0.04%
Summary	1.0000s	0.9954s	-0.46%	1 byte	1.00 bytes	0.08%	1 byte	1.00 bytes	0.04%

[nnethercote]

rustc-perf is our gold standard. If that shows regressions on CI, that takes precedence over local measurements.

[Zoxc]

I'll take an up to 0.45% (mean 0.1%) instruction regression to fix the dep graph size regression though.

[rust-bors]

☔ The latest upstream changes (presumably #152516) made this pull request unmergeable. Please resolve the merge conflicts.