RFR: 8368251: Parallel: Refactor lgrp_id used in MutableNUMASpace [v2]
Joel Sikström
jsikstro at openjdk.org
Tue Sep 23 08:58:19 UTC 2025
> 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`
Joel Sikström has updated the pull request incrementally with one additional commit since the last revision:
Don't set lgrp_id on Windows since we don't support NUMA there
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/27424/files
- new: https://git.openjdk.org/jdk/pull/27424/files/980d4684..d8dcd72a
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=27424&range=01
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=27424&range=00-01
Stats: 8 lines in 1 file changed: 0 ins; 8 del; 0 mod
Patch: https://git.openjdk.org/jdk/pull/27424.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/27424/head:pull/27424
PR: https://git.openjdk.org/jdk/pull/27424
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