Integrated: 8368251: Parallel: Refactor lgrp_id used in MutableNUMASpace

[Joel Sikström]

On Mon, 22 Sep 2025 11:42:39 GMT, Joel Sikström <jsikstro at openjdk.org> wrote:

> Hello,
> 
> There are multiple cases which handle if the locality group (lgrp) id is negative (-1) in Parallel, specifically in MutableNUMASpace. -1 was historically used to indicate that the hardware topology has changed and that the lgrp id needs to be updated. This is no longer the case, since HotSpot doesn't support CPU/NUMA hotplugging, and the last piece of code setting the lgrp id to -1 was removed in [JDK-8301149](https://bugs.openjdk.org/browse/JDK-8301149).
> 
> I propose we simplify the code a bit by not handling edge cases where the lgrp id is -1 and removing os::numa_has_group_homing(), which always return false
> 
> Testing:
>  * Running through Oracle's tier 1-4
>  * Local NUMA testing tier1-4 with `-XX:+UseParallelGC -XX:+UseNUMA`

This pull request has now been integrated.

Changeset: d407ef65
Author:    Joel Sikström <jsikstro at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/d407ef651032de687e3d4a2a2db211cab1016676
Stats:     125 lines in 10 files changed: 9 ins; 96 del; 20 mod

8368251: Parallel: Refactor lgrp_id used in MutableNUMASpace

Reviewed-by: lkorinth, ayang, tschatzl

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PR: https://git.openjdk.org/jdk/pull/27424