RFR: 8370947: Mitigate Neoverse-N1 erratum 1542419 negative impact on GenZGC performance [v2]

[Andrew Haley]

On Sun, 23 Nov 2025 10:32:15 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

> > If I understand correctly, the whole icache is flushed, so the actual nmethod* is irrelevant.  So instead of         `ICacheInvalidationContext icic(nm)` for every different "nm", can't we just do `ICacheInvalidationContext icic(true)` one time, outside the nmethod loop?
> 
> We can't disarm an nmethod before flushing the instructions.

Sure, but you can't patch an nmethod until every thread that might be executing it has stopped. So if the threads are all stopped, why not postpone the disarmament until the end, just before you flush?

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PR Comment: https://git.openjdk.org/jdk/pull/28328#issuecomment-3568021134