RFR: 8316694: Implement relocation of nmethod within CodeCache [v27]
Chad Rakoczy
duke at openjdk.org
Tue Jun 17 20:40:57 UTC 2025
> This PR introduces a new function to replace nmethods, addressing [JDK-8316694](https://bugs.openjdk.org/browse/JDK-8316694). It enables the creation of new nmethods from existing ones, allowing method relocation in the code heap and supporting [JDK-8328186](https://bugs.openjdk.org/browse/JDK-8328186).
>
> When an nmethod is replaced, a deep copy is performed. The corresponding Java method is updated to reference the new nmethod, while the old one is marked as unused. The garbage collector handles final cleanup and deallocation.
>
> This change does not modify existing code paths and therefore does not benefit much from existing tests. New tests were created and confirmed to pass on x64/aarch64 for slowdebug/fastdebug/release.
Chad Rakoczy has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 83 commits:
- Merge remote-tracking branch 'origin/master' into JDK-8316694-Final
- Only check branch distance for aarch64 and riscv
- Move far branch fix to fix_relocation_after_move
- Move far branch fix to fix_relocation_after_move
- Add test to verify JVMTI events during nmethod relocation
- Log relocated nmethod
- Publish JVMTI events
- Fix test copywrite
- Update immutable_data_references naming
- Update ImmutableDataReferences
- ... and 73 more: https://git.openjdk.org/jdk/compare/afa52e46...6173fdbb
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Changes: https://git.openjdk.org/jdk/pull/23573/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23573&range=26
Stats: 1603 lines in 23 files changed: 1567 ins; 1 del; 35 mod
Patch: https://git.openjdk.org/jdk/pull/23573.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/23573/head:pull/23573
PR: https://git.openjdk.org/jdk/pull/23573
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