RFR: 8220566: AArch64: Set default vm features for Ampere eMAG CPUs

Andrew Dinn adinn at redhat.com
Thu Mar 14 09:03:11 UTC 2019

Hi Patrick,

On 14/03/2019 04:05, Patrick Zhang OS wrote:
> I added below comments in JIRA, also copied here. Thanks for your
> review.
> https://bugs.openjdk.java.net/browse/JDK-8220566?focusedCommentId=14251292&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14251292
>  These three flags had been verified on Ampere eMAG platform with a
> couple of benchmarks and apps AvoidUnalignedAccesses=TRUE,
> UseSIMDForMemoryOps=TRUE can bring positive impact consistently,
> since access to odd alignment memory is not what we expect, and simd
> instructions replacement for mem/array copying practically helps
> performance. While for UseSIMDForArrayEquals=TRUE (default), I am not
> quite sure yet what took more execution time, either ld1 or umov, or
> the sequence generated inside generate_large_array_equals_loop_simd.
> Therefore I make it FALSE within a stricter condition for CPU
> revisions I have so far.

Thank you for making your decisions clear. I am happy to accept your
choice of defaults so this patch can be pushed. Do you need me to do
that for you?


Andrew Dinn
Senior Principal Software Engineer
Red Hat UK Ltd
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