Reduce code size of `thread::set_current` #123356

joboet · 2024-04-02T09:31:13Z

#123265 introduced a rather large binary size regression, because it added an unwrap() call on a Result<(), Thread>, which in turn pulled its rather heavy Debug implementation. This PR fixes this by readding the rtassert! that was removed.

rustbot · 2024-04-02T09:31:22Z

r? @ChrisDenton

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library/std/src/thread/mod.rs

Kobzol · 2024-04-02T09:37:00Z

@bors try @rust-timer queue

Reduce code size of `thread::set_current` rust-lang#123265 introduced a rather large binary size regression, because it added an `unwrap()` call on a `Result<(), Thread>`, which in turn pulled its rather heavy `Debug` implementation. This PR fixes this by readding the `rtassert!` that was removed.

bors · 2024-04-02T09:38:09Z

⌛ Trying commit b5ccebf with merge ae182b1...

Noratrieb · 2024-04-02T09:49:50Z

I think the push cancelled the try build.
@bors try @rust-timer queue

Reduce code size of `thread::set_current` rust-lang#123265 introduced a rather large binary size regression, because it added an `unwrap()` call on a `Result<(), Thread>`, which in turn pulled its rather heavy `Debug` implementation. This PR fixes this by readding the `rtassert!` that was removed.

bors · 2024-04-02T09:51:00Z

⌛ Trying commit e7b5730 with merge c38c6c9...

bors · 2024-04-02T11:29:49Z

☀️ Try build successful - checks-actions
Build commit: c38c6c9 (c38c6c92fe6cc168e48deb51b39da5367f0b340e)

rust-timer · 2024-04-02T15:14:59Z

Finished benchmarking commit (c38c6c9): comparison URL.

Overall result: ❌ regressions - 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 a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.3%	[3.3%, 3.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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

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)	-0.1%	[-0.2%, -0.0%]	12
Improvements ✅ (secondary)	-0.9%	[-1.3%, -0.2%]	39
All ❌✅ (primary)	-0.1%	[-0.2%, -0.0%]	12

Bootstrap: 666.146s -> 668.198s (0.31%)
Artifact size: 315.65 MiB -> 315.74 MiB (0.03%)

workingjubilee · 2024-04-02T17:51:52Z

That is ~exactly the number of things buffed as were regressed, and by about as much. Seems to patch the original completely. Nice work!

@bors r+

bors · 2024-04-02T17:51:54Z

📌 Commit e7b5730 has been approved by workingjubilee

It is now in the queue for this repository.

workingjubilee · 2024-04-02T17:53:39Z

Wait.

@bors r-

@joboet Can you add a comment noting the use of rtabort! is load-bearing for about 5kb all on its lonesome?

joboet · 2024-04-03T12:34:38Z

Sure, done!

@bors r=workingjubilee

library/std/src/thread/mod.rs

joboet · 2024-04-04T09:53:00Z

@bors r-
If some code running pre-main accesses thread::current, this will abort because the thread will be initialized before we get a chance to do so in init.

RalfJung · 2024-04-04T09:55:50Z

That just means pre-main code should not do that...?
We control all pre-main code.

joboet · 2024-04-04T09:58:16Z

No, there are ways and means to get around that. We document our limitations here, thread::current before main isn't on the list. And considering how simple it is to support that, I don't see why we shouldn't. I've changed the abort to a noop now.

RalfJung · 2024-04-04T10:04:00Z

Silently dropping this seems rather suspicious but I don't have any overview over the lifecycle of this variable.

joboet · 2024-04-04T10:09:12Z

We normally call this in rt::init and the thread main function. For threads, nothing can run before it that we don't control, but for main you could use some linker magic. If you then access thread::current, it gets initialized to some default value (so that it can be used in foreign threads), meaning that the set_current in rt::init will abort.

Anyway, I don't feel any particular way about this, as long as we don't unwrap on a Result<(), Thread>, because that leads to the code size issues this PR aimed to solve.

RalfJung · 2024-04-04T11:04:18Z

If you then access thread::current, it gets initialized to some default value (so that it can be used in foreign threads), meaning that the set_current in rt::init will abort.

What's the consequence of discarding it the 2nd time? Just a different thread name or anything more serious?

If you change it like this IMO it should be called try_set_current or so.

workingjubilee · 2024-04-05T18:09:26Z

💀 what

joboet · 2024-04-08T10:18:54Z

Sorry for the confusion, I totally derailed the conversation. The PR is now back to the approved state, with an updated abort message as Ralf suggested.
@rustbot ready

ChrisDenton · 2024-05-04T07:40:33Z

Sorry for the confusion, I totally derailed the conversation. The PR is now back to the approved state, with an updated abort message as Ralf suggested.

lgtm

@bors r+ rollup

bors · 2024-05-04T07:40:36Z

📌 Commit 37c1758 has been approved by ChrisDenton

It is now in the queue for this repository.

…nton Reduce code size of `thread::set_current` rust-lang#123265 introduced a rather large binary size regression, because it added an `unwrap()` call on a `Result<(), Thread>`, which in turn pulled its rather heavy `Debug` implementation. This PR fixes this by readding the `rtassert!` that was removed.

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#123356 (Reduce code size of `thread::set_current`) - rust-lang#124159 (Move thread parking to `sys::sync`) - rust-lang#124293 (Let miri and const eval execute intrinsics' fallback bodies) - rust-lang#124500 (lldb-formatters: Use StdSliceSyntheticProvider for &str) - rust-lang#124677 (Set non-leaf frame pointers on Fuchsia targets) - rust-lang#124692 (We do not coerce `&mut &mut T -> *mut mut T`) r? `@ghost` `@rustbot` modify labels: rollup

…iaskrgr Rollup of 8 pull requests Successful merges: - rust-lang#123356 (Reduce code size of `thread::set_current`) - rust-lang#124159 (Move thread parking to `sys::sync`) - rust-lang#124293 (Let miri and const eval execute intrinsics' fallback bodies) - rust-lang#124677 (Set non-leaf frame pointers on Fuchsia targets) - rust-lang#124692 (We do not coerce `&mut &mut T -> *mut mut T`) - rust-lang#124698 (Rewrite `rustdoc-determinism` test in Rust) - rust-lang#124700 (Remove an unnecessary cast) - rust-lang#124701 (Docs: suggest `uN::checked_sub` instead of check-then-unchecked) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#123356 - joboet:set_current_size, r=ChrisDenton Reduce code size of `thread::set_current` rust-lang#123265 introduced a rather large binary size regression, because it added an `unwrap()` call on a `Result<(), Thread>`, which in turn pulled its rather heavy `Debug` implementation. This PR fixes this by readding the `rtassert!` that was removed.

rustbot assigned ChrisDenton Apr 2, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 2, 2024

joboet mentioned this pull request Apr 2, 2024

Refactor stack overflow handling #123265

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Noratrieb reviewed Apr 2, 2024

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 2, 2024

std: reduce code size of set_current

e7b5730

joboet force-pushed the set_current_size branch from b5ccebf to e7b5730 Compare April 2, 2024 09:41

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std: add comment about abort motivation

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std: update abort message in thread::set_current

37c1758

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Apr 8, 2024

joboet force-pushed the set_current_size branch from 957c442 to 37c1758 Compare April 8, 2024 10:18

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matthiaskrgr mentioned this pull request May 4, 2024

Rollup of 6 pull requests #124697

Closed

matthiaskrgr mentioned this pull request May 4, 2024

Rollup of 8 pull requests #124703

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bors merged commit b8fa047 into rust-lang:master May 4, 2024
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joboet deleted the set_current_size branch May 4, 2024 16:56

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Reduce code size of `thread::set_current` #123356

Reduce code size of `thread::set_current` #123356

joboet commented Apr 2, 2024 •

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Reduce code size of thread::set_current #123356

Reduce code size of thread::set_current #123356

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rust-timer commented Apr 2, 2024

Overall result: ❌ regressions - no action needed

Instruction count

Max RSS (memory usage)

Cycles

Binary size

workingjubilee commented Apr 2, 2024

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Reduce code size of `thread::set_current` #123356

Reduce code size of `thread::set_current` #123356

joboet commented Apr 2, 2024 •

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