RFR: 8370947: Mitigate Neoverse-N1 erratum 1542419 negative impact on GenZGC performance [v6]

[Evgeny Astigeevich]

On Wed, 26 Nov 2025 09:04:19 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> Evgeny Astigeevich has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Remove redundant include
>>  - Move ICacheInvalidationContext::pd_ to icache_linux_aarch64
>
> Some style comments.

@xmas92 
I fixed regressions for Java methods without field accesses I saw:
- `-XX:+NeoverseN1Errata1542419` before the fix

Benchmark                       (accessedFieldCount)  (methodCount)  Mode  Cnt    Score    Error  Units
GCPatchingNmethodCost.fullGC                       0           5000  avgt    3   88.865 ± 19.299  ms/op
GCPatchingNmethodCost.systemGC                     0           5000  avgt    3   90.572 ± 14.750  ms/op
GCPatchingNmethodCost.youngGC                      0           5000  avgt    3   10.219 ±  0.877  ms/op


- `-XX:+NeoverseN1Errata1542419` after the fix

Benchmark                       (accessedFieldCount)  (methodCount)  Mode  Cnt   Score    Error  Units
GCPatchingNmethodCost.fullGC                       0           5000  avgt    3  60.847 ± 23.735  ms/op
GCPatchingNmethodCost.systemGC                     0           5000  avgt    3  62.338 ±  5.663  ms/op
GCPatchingNmethodCost.youngGC                      0           5000  avgt    3   4.956 ±  1.440  ms/op


- `-XX:-NeoverseN1Errata1542419`

Benchmark                       (accessedFieldCount)  (methodCount)  Mode  Cnt   Score    Error  Units
GCPatchingNmethodCost.fullGC                       0           5000  avgt    3  67.144 ± 15.187  ms/op
GCPatchingNmethodCost.systemGC                     0           5000  avgt    3  70.181 ± 30.271  ms/op
GCPatchingNmethodCost.youngGC                      0           5000  avgt    3   7.906 ±  2.118  ms/op


I'll check SpecJVM as well.

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PR Comment: https://git.openjdk.org/jdk/pull/28328#issuecomment-3582302388