RFR: 8320318: ObjectMonitor Responsible thread [v4]
Fredrik Bredberg
fbredberg at openjdk.org
Wed Sep 25 13:54:07 UTC 2024
> Removed the concept of an ObjectMonitor Responsible thread.
>
> The reason to have an ObjectMonitor Responsible thread was to avoid threads getting stranded due to a hole in the successor protocol. This hole was there because adding the necessary memory barrier was considered too expensive some 20 years ago.
>
> The ObjectMonitor Responsible thread code adds complexity, and doing timed parks just to avoid getting stranded is not the way forward. More info about the problems with the ObjectMonitor responsible thread can be found in [JDK-8320318](https://bugs.openjdk.org/browse/JDK-8320318).
>
> After removing the ObjectMonitor Responsible thread we see increased performance on all supported platforms except Windows. [JDK-8339730](https://bugs.openjdk.org/browse/JDK-8339730) has been created to handle this.
>
> Passes tier1-tier7 on supported platforms.
> x64, AArch64, Riscv64, ppc64le and s390x passes ok on the test/micro/org/openjdk/bench/vm/lang/LockUnlock.java test.
> Arm32 and Zero doesn't need any changes as far as I can tell.
Fredrik Bredberg has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 14 commits:
- Update three, after the review
- Merge branch 'master' into 8320318_objectmon_responsible_thread
- Update two, after the review
- Update one, after the review
- Small fixes before the review
- Merge branch 'master' into 8320318_objectmon_responsible_thread
- Merge branch 'master' into 8320318_objectmon_responsible_thread
- Removed _Responsible
- Fixed s390
- Fixed legacy locking
- ... and 4 more: https://git.openjdk.org/jdk/compare/0f253d11...8140570f
-------------
Changes: https://git.openjdk.org/jdk/pull/19454/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19454&range=03
Stats: 720 lines in 14 files changed: 302 ins; 288 del; 130 mod
Patch: https://git.openjdk.org/jdk/pull/19454.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/19454/head:pull/19454
PR: https://git.openjdk.org/jdk/pull/19454
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