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

[Patrick Zhang OS]

Hi Andrew,
Sure, please, thank you very much for sponsoring this.

Regards
Patrick

-----Original Message-----
From: Andrew Dinn <adinn at redhat.com> 
Sent: Thursday, March 14, 2019 5:03 PM
To: Patrick Zhang OS <patrick at os.amperecomputing.com>
Cc: aarch64-port-dev at openjdk.java.net; hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR: 8220566: AArch64: Set default vm features for Ampere eMAG CPUs

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=1425
> 1292&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabp
> anel#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?

regards,


Andrew Dinn
-----------
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