[jdk25u-dev] RFR: 8369611: Remove safepoint synchronization from ParallelScavengeHeap and SerialHeap

[Goetz Lindenmaier]

On Thu, 8 Jan 2026 16:02:50 GMT, Roland Mesde <duke at openjdk.org> wrote:

> Backporting JDK-8369611: Remove safepoint synchronization from ParallelScavengeHeap and SerialHeap
> 
> This PR removes unnecessary conditional STS (Safepoint Thread Synchronization) code from ParallelScavengeHeap and SerialHeap. The cleanup is possible because StringDedup threads are now derived from JavaThread (changed in JDK-8369392), eliminating the need for special conditional synchronization logic that was previously required when StringDedup threads had different threading characteristics.
> 
> This backport has internal demand.
> 
> Ran related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:
> 
> make test TEST=test/hotspot/jtreg/vmTestbase/gc
> 
> Results attached:
> 
> [windows-x64-specific-test.log](https://github.com/user-attachments/files/24510510/windows-x64-specific-test.log)
> [macos-aarch64-specific-test.log](https://github.com/user-attachments/files/24510512/macos-aarch64-specific-test.log)
> [linux-x64-specific-test.log](https://github.com/user-attachments/files/24510513/linux-x64-specific-test.log)
> [linux-aarch64-specific-test.log](https://github.com/user-attachments/files/24510514/linux-aarch64-specific-test.log)

Hi Roland, 
you are backporting enhancements and similar. As they are in GC, very central, I would prefer that these rather go to April or July updates, so that they are tested in 26 for some time.

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PR Comment: https://git.openjdk.org/jdk25u-dev/pull/136#issuecomment-3750435628