8294845: Make globals accessed by G1 young gen revising atomic

[tschatzl]

Hi all,

can I have reviews for this cleanup that makes a few globals accessed by G1Policy::update_young_length_bounds "atomic" as per style guide? Basically there are a few variables that are changed by young gen size revising that are read concurrently, and to indicate that, this change decorates them with the Atomic accessor functions.

This is no attempt to fix any visibility races that (already, pre-existing) occur when these values are written and read; I think all of these are benign and can at most lead to having garbage collections that are "too late" or "too early" due to that. However all the young gen length revising, particularly in presence of the gclocker, is and has always been a best effort approach as far as I could ever tell.

Testing: gha

Thanks,
Thomas

---

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Issue

• JDK-8294845: Make globals accessed by G1 young gen revising atomic

Reviewers

• Ivan Walulya (@walulyai - Reviewer) ⚠️ Review applies to 77af16da
• Kim Barrett (@kimbarrett - Reviewer) ⚠️ Review applies to 77af16da

Reviewing

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[mlbridge]

Webrevs

• 01: Full - Incremental (c2825bd3)
• 00: Full (77af16da)

[openjdk]

@tschatzl This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8294845: Make globals accessed by G1 young gen revising atomic

Reviewed-by: iwalulya, kbarrett

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At the time when this comment was updated there had been 74 new commits pushed to the master branch:

• 8de3eda: 8295476: Split G1 cost per byte predictor on gc phase
• 2634eff: 8295646: Ignore zero pairs in address descriptors read by dwarf parser
• 50d91a3: 8057113: (fs) Path should have a method to obtain the filename extension
• d17bf51: 8295914: Add a header to generated HTML files in specs
• 9911405: 8282958: Rendering issues of borders, TextFields on Windows High-DPI systems
• 2fb64a4: 8296162: [aarch64] Remove unused Address::_is_lval
• 15b8b45: 8296161: [aarch64] Remove unused "pcrel" addressing mode tag
• f829b5a: 8280378: [IR Framework] Support IR matching for different compile phases
• da0ae51: 8296167: test/langtools/tools/jdeps/jdkinternals/ShowReplacement.java failing after JDK-8296072
• 0d0bd7b: 8296072: CertAttrSet::encode and DerEncoder::derEncode should write into DerOutputStream
• ... and 64 more: https://git.openjdk.org/jdk/compare/706d1b7508af58f7ed669bde4820ec9f80f58607...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[kimbarrett]

Looks good.

[tschatzl]

Thanks @kimbarrett @walulyai for your reviews
/integrate

[openjdk]

Going to push as commit 6626a29.
Since your change was applied there have been 80 commits pushed to the master branch:

• dac6ecc: 8295990: Improve make handling of strip flags
• 38c1f2a: 8296130: G1: Remove G1YoungCollector::_target_pause_time_ms
• 2bd24c4: 8295968: RISC-V: Rename some assembler intrinsic functions for RVV 1.0
• 1a58cb1: 8233697: CHT: Iteration parallelization
• 7619602: 8296136: Use correct register in aarch64_enc_fast_unlock()
• 47d513b: 8252075: Documentation error in LayoutManager2 interface
• 8de3eda: 8295476: Split G1 cost per byte predictor on gc phase
• 2634eff: 8295646: Ignore zero pairs in address descriptors read by dwarf parser
• 50d91a3: 8057113: (fs) Path should have a method to obtain the filename extension
• d17bf51: 8295914: Add a header to generated HTML files in specs
• ... and 70 more: https://git.openjdk.org/jdk/compare/706d1b7508af58f7ed669bde4820ec9f80f58607...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tschatzl Pushed as commit 6626a29.

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