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Change memory ordering in System wrapper example #106599

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merged 1 commit into from
Apr 27, 2023

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MikailBag
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Currently, the SeqCst ordering is used, which seems unnecessary:

  • Even Relaxed ordering guarantees that all updates are atomic and are executed in total order
  • User code only reads atomic for monitoring purposes, no "happens-before" relationships with actual allocations and deallocations are needed for this

If argumentation above is correct, I propose changing ordering to Relaxed to clarify that no synchronization is required here, and improve performance (if somebody copy-pastes this example into their code).

Currently, the `SeqCst` ordering is used, which seems unnecessary:
+ Even `Relaxed` ordering guarantees that all updates are atomic and are executed in total order
+ User code only reads atomic for monitoring purposes, no "happens-before" relationships with actual allocations and deallocations are needed for this

If argumentation above is correct, I propose changing ordering to `Relaxed` to clarify that no synchronization is required here, and improve performance (if somebody copy-pastes this example into their code).
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rustbot commented Jan 8, 2023

r? @m-ou-se

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@rustbot 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 Jan 8, 2023
@MikailBag MikailBag marked this pull request as ready for review January 8, 2023 20:37
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rustbot commented Jan 8, 2023

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

  • Stabilizing library features
  • Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
  • Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
  • Changing public documentation in ways that create new stability guarantees
  • Changing observable runtime behavior of library APIs

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jyn514 commented Apr 27, 2023

This looks correct to me.

@bors r+ rollup

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bors commented Apr 27, 2023

📌 Commit 7b9f644 has been approved by jyn514

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 27, 2023
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Apr 27, 2023
Change memory ordering in System wrapper example

Currently, the `SeqCst` ordering is used, which seems unnecessary:
+ Even `Relaxed` ordering guarantees that all updates are atomic and are executed in total order
+ User code only reads atomic for monitoring purposes, no "happens-before" relationships with actual allocations and deallocations are needed for this

If argumentation above is correct, I propose changing ordering to `Relaxed` to clarify that no synchronization is required here, and improve performance (if somebody copy-pastes this example into their code).
bors added a commit to rust-lang-ci/rust that referenced this pull request Apr 27, 2023
…iaskrgr

Rollup of 9 pull requests

Successful merges:

 - rust-lang#105745 (docs(std): clarify remove_dir_all errors)
 - rust-lang#106456 (Correct `std::prelude` comment)
 - rust-lang#106599 (Change memory ordering in System wrapper example)
 - rust-lang#110838 (More `Typefoldable`/`TypeVisitable` cleanups)
 - rust-lang#110851 (compiletest: emit assembly-output header in error)
 - rust-lang#110853 (compiletest: add bpf-linker assembly support)
 - rust-lang#110878 (Add `known-bug` tests for 4 unsound issues)
 - rust-lang#110886 (`DepGraph` cleanups)
 - rust-lang#110905 (Remove invalid value from scraped-examples.md)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 2148942 into rust-lang:master Apr 27, 2023
@rustbot rustbot added this to the 1.71.0 milestone Apr 27, 2023
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5 participants