RFR: 8277617: Adjust AVX3Threshold for copy/fill stubs

[Jie Fu]

On Tue, 23 Nov 2021 06:05:48 GMT, Jie Fu <jiefu at openjdk.org> wrote:

>> @sviswa7 that further restriction and an explanatory comment would be appreciated. Thanks.
>
>> @dholmes-ora We see about 25% gain on a micro on our latest platform. There is no cpuid bit for this, so the closest was to check for the new serialize ISA supported on this platform.
> 
> It would be better to add a jmh test for this opt.
> Thanks.

> @DamonFool There are jmh tests for Arraycopy in test/micro/org/openjdk/bench/java/lang/Arraycopy.java.

So how about posting the detailed perf data before and after this patch?
Thanks.

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PR: https://git.openjdk.java.net/jdk/pull/6512