8368251: Parallel: Refactor lgrp_id used in MutableNUMASpace

[jsikstro]

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.

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

---

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Issue

• JDK-8368251: Parallel: Refactor lgrp_id used in MutableNUMASpace (Enhancement - P4)

Reviewers

• Albert Mingkun Yang (@albertnetymk - Reviewer)

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8368251: Parallel: Refactor lgrp_id used in MutableNUMASpace

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[jsikstro]

/label remove hotspot
/label add hotspot-gc

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The hotspot label was successfully removed.

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@jsikstro
The hotspot-gc label was successfully added.

[jsikstro]

I'm a bit hesistant to remove this code from Windows since I have no way to test this. However, since we set UseNUMA = false early on initialization on Windows, Paralell should never start with NUMA enabled, so this code should effectively have no effect.