Integrated: 8320318: ObjectMonitor Responsible thread

[Fredrik Bredberg]

On Wed, 29 May 2024 12:58:02 GMT, Fredrik Bredberg <fbredberg at openjdk.org> wrote:

> 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.

This pull request has now been integrated.

Changeset: 180affc5
Author:    Fredrik Bredberg <fbredberg at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/180affc5718c9bf2f009d6a7aa129cc36335384a
Stats:     722 lines in 14 files changed: 301 ins; 284 del; 137 mod

8320318: ObjectMonitor Responsible thread

Reviewed-by: aboldtch, coleenp, pchilanomate, eosterlund

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PR: https://git.openjdk.org/jdk/pull/19454