RFR: 8339573: Update CodeCacheSegmentSize and CodeEntryAlignment for ARM

[Vladimir Kozlov]

On Wed, 11 Sep 2024 14:45:15 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

>> Were performance runs made with CodeEntryAlignment set to other than 64 or 16?  It seems like the other choices (32, 128, are there others that make sense?) should be tried.
>
>> Were performance runs made with CodeEntryAlignment set to other than 64 or 16? It seems like the other choices (32, 128, are there others that make sense?) should be tried.
> 
> Here are rough neoverse-v2 numbers:
> JmhDotty (-XX:CodeEntryAlignment=16) 701.93 ± 5.00 ms/op
> JmhDotty (-XX:CodeEntryAlignment=32) 703.56 ± 5.15 ms/op
> JmhDotty (-XX:CodeEntryAlignment=64) 704.46 ± 5.18 ms/op
> JmhDotty (-XX:CodeEntryAlignment=128) 703.71 ± 5.17 ms/op

Hi @bulasevich 
We got significant (few percents) regression when testing -XX:CodeCacheSegmentSize=64 -XX:CodeEntryAlignment=16 on Ampere system which has N1 CPU.  
Is it possible to not set CodeEntryAlignment=16 for N1? 
May be even limit it for V1 and V2 only?

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PR Comment: https://git.openjdk.org/jdk/pull/20864#issuecomment-2347402012