RFR: 8342382: Implement JEP 522: G1 GC: Improve Throughput by Reducing Synchronization [v54]

[Thomas Schatzl]

On Wed, 10 Sep 2025 07:53:15 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> We would like to finally wrap up this PR as we are about to Propose To Target [JEP 522](openjdk.org/jeps/522) to JDK 26, so it would be nice to get re-reviews from the reviewers that already signed it off if you think it is useful.
>> 
>> Nothing much changed actually for months now, particularly in the area of target-specific support, but maybe one more rerun on the more exotic platforms (AIX/PPC, RISC-V) just in case would be fine.
>> 
>> Internally it went through Oracle's tier1-8 without any issue again (that is revision https://github.com/openjdk/jdk/pull/23739/commits/b3873d66cd43518d5dc71e060fc52a13372dbfa5, but the changes since then were very cosmetic).
>
>> Hi @tschatzl : I witnessed some conflicts when applying this on latest jdk head. Maybe you can do another merge and rebase? I can help rerun the tests on RISC-V. (Note that there is one failing test: `test/hotspot/jtreg/gtest/GTestWrapper.java` if I use the same base as in your repo, and that issue has been resolved by [JDK-8366897](https://bugs.openjdk.org/browse/JDK-8366897))
> 
> Merged. Thanks for another round of testing (also to @TheRealMDoerr).

> > Hi @tschatzl, I see one build failure on s390x,
> > ```
> > #
> > # A fatal error has been detected by the Java Runtime Environment:
> > #
> > #  SIGILL (0x4) at pc=0x000003ffaad14a42, pid=1801882, tid=1801914
> > #
> > # JRE version: OpenJDK Runtime Environment (26.0) (fastdebug build 26-internal-adhoc.amit.jdk)
> > # Java VM: OpenJDK 64-Bit Server VM (fastdebug 26-internal-adhoc.amit.jdk, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-s390x)
> > # Problematic frame:
> > # V  [libjvm.so+0x414a46]  BarrierSetNMethod::set_guard_value(nmethod*, int, int)+0xfe
[...]
> >   
> > I am working on this on priority, but just in case you want to merge it, I will open another issue and push the fix.
> 
> Seems like build failure came from one change merged yesterday- #26399, I am working on it and created https://bugs.openjdk.org/browse/JDK-8367325

This should definitely be caused by that other change. Apologies for the trouble.

Thank you for working on this.

Thomas

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PR Comment: https://git.openjdk.org/jdk/pull/23739#issuecomment-3274535127