[perf] More span update benchmarking

[petrochenkov]

#126544 (comment)

[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

[petrochenkov]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 7e4f176 with merge 725e23c...

[petrochenkov]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 91d05ba with merge 0659a9a...

[bors]

☀️ Try build successful - checks-actions
Build commit: 0659a9a (0659a9a7205e944bd6c6f9b79411797af5772418)

[rust-timer]

Finished benchmarking commit (0659a9a): comparison URL.

Overall result: ❌✅ regressions and improvements - 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.

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 a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.3%, 0.4%]	3
Regressions ❌ (secondary)	2.2%	[1.3%, 3.6%]	6
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.3%]	1
Improvements ✅ (secondary)	-0.3%	[-0.6%, -0.2%]	15
All ❌✅ (primary)	0.2%	[-0.3%, 0.4%]	4

Max RSS (memory usage)

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

Cycles

Results (secondary -2.3%)

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.3%, -2.3%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 669.445s -> 669.827s (0.06%)
Artifact size: 320.51 MiB -> 320.50 MiB (-0.00%)

[nnethercote]

Nice simplification.

@bors r+

[bors]

📌 Commit 91d05ba has been approved by nnethercote

It is now in the queue for this repository.

[bors]

⌛ Testing commit 91d05ba with merge 737e423...

[bors]

☀️ Test successful - checks-actions
Approved by: nnethercote
Pushing 737e423 to master...

[petrochenkov]

@nnethercote
I never intended to merge this, it was just an experiment, and I didn't test everything I wanted.
I've even explicitly set the label to waiting on author.

[nnethercote]

Waiting on author is not an obvious signal, it's very easy to overlook. Next time I suggest one or more of the following.

• Mark it as a draft.
• Put "[DO NOT MERGE]" or "[EXPERIMENT]" or something more obvious in the title.
• Write a better PR description.
• Use r? @ghost as the reviewer.

[petrochenkov]

Labels are important, most important from what you've listed, and they also subsume the draft mark entirely as a better tool.
Merging a PR without a description is also pretty questionable.
I guess I'll use more big letters as a precaution next time.

[petrochenkov]

issue-58319 has a very significant regression (5-10x significance factor), so I expected it to have some unusual statistics, e.g. many PartiallyInterneds.
But that's not the case, all the updates in that test are still InlineCtxts!
Apparently it's just the same kind of inlining noise as in other cases.

Upd: same for bitmaps.
So it's fine to merge the change itself, I'll just need to add some explanatory comments.

[rust-timer]

Finished benchmarking commit (737e423): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.3%, 0.4%]	5
Regressions ❌ (secondary)	2.3%	[1.4%, 3.6%]	6
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.3%]	1
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.2%]	14
All ❌✅ (primary)	0.2%	[-0.3%, 0.4%]	6

Max RSS (memory usage)

Results (primary -4.4%)

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)	-4.4%	[-4.4%, -4.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-4.4%	[-4.4%, -4.4%]	1

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: 671.082s -> 670.264s (-0.12%)
Artifact size: 320.51 MiB -> 320.46 MiB (-0.02%)

[lqd]

Labels are important, most important from what you've listed, and they also subsume the draft mark entirely as a better tool.

IIRC bors will not merge a PR in draft status, or a PR with WIP in its title (maybe even with DO NOT MERGE), so these are preferred to labels as it’s not possible for this situation to happen