RFR: JDK-8310502 : Optimization for j.l.Long.fastUUID() [v25]

[Chen Liang]

On Mon, 26 Jun 2023 09:57:31 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> By optimizing the implementation of java.lang.Long#fastUUID, the performance of the java.util.UUID#toString method can be significantly improved.
>> 
>> The following are the test results of JMH: 
>> 
>> Benchmark                     Mode  Cnt      Score      Error   Units
>> UUIDUtilsBenchmark.new       thrpt    5  92676.550 ±  292.213  ops/ms
>> UUIDUtilsBenchmark.original  thrpt    5  37040.165 ± 1023.532  ops/ms
>
> 温绍锦 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   use ISO_8859_1.INSTANCE directly instead of StandardCharsets.ISO_8859_1

I think we can work towards only optimizing the (compat string) case. Many other optimization patches improve the performance of certain scenarios without affecting, or at a slight cost for, other scenarios. I think this patch would be acceptable as long as the non-compat case doesn't get a significant overhead compared to the baseline.

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PR Comment: https://git.openjdk.org/jdk/pull/14578#issuecomment-1607711346