RFR: 8353500: [s390x] Intrinsify Unsafe::setMemory [v4]

[Ulrich Weigand]

On Tue, 13 May 2025 09:59:49 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> The invariant on other platforms is that all Bytes before the non-writable address have been written when hitting a signal. I don' know if that is really required on s390. It may be a risk to use a different behavior. The code can be used to write memory mapped files or other stuff. If this behavior is not required, why not use mvc always?

I thought the reason for not using mvc always is atomicity within array elements?  That is, if you're writing an array of 4- or 8-byte values, than change to every one of those array elements should be atomic w.r.t. other CPUs.  If that is true, you cannot use mvc.  (However, that requirement would not be relevant for arrays of 1-byte values.)

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PR Comment: https://git.openjdk.org/jdk/pull/24480#issuecomment-2876031937