RFR: 8339573: Update CodeCacheSegmentSize and CodeEntryAlignment for ARM

[Boris Ulasevich]

On Thu, 12 Sep 2024 23:23:51 GMT, Vladimir Kozlov <kvn 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.
>> 
>> 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?

@vnkozlov Many thanks!
Do you reproduce the regression on a public benchmark that I can also try?
Now I restrict CodeEntryAlignment=16 for V1 and V2 only. And I restart my performance tests.

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PR Comment: https://git.openjdk.org/jdk/pull/20864#issuecomment-2348852151