RFR: 8336856: Optimize String Concat [v15]

[Shaojin Wen]

On Thu, 25 Jul 2024 10:15:20 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add benchmark
>
> test/micro/org/openjdk/bench/java/lang/StringConcatGenerate.java line 47:
> 
>> 45: @Measurement(iterations = 5, time = 1000, timeUnit = TimeUnit.MILLISECONDS)
>> 46: @Fork(value = 3, jvmArgsAppend = "-Djava.lang.invoke.StringConcat.highArityThreshold=0")
>> 47: public class StringConcatGenerate extends StringConcat {
> 
> Adding a subclass with an overridden `@Fork` to pass a different `jvmArgsAppend` is a reasonable trick, but could be moved to a nested class within `StringConcat` to keep it in the same context. I'm not sure if this micro brings a persistent added value, though: for experimentation we can just run `StringConcat` with different `-Djava.lang.invoke.StringConcat.highArityThreshold` settings, while for continuous regression testing we're more interested in validating the default settings. Supplying the new `main` method doesn't add anything here, either, since a standalone execution wouldn't pick up the `jvmArgsAppend` value.

I have removed the newly added micro benchmark. But I don't know how to add jvmArgs in make test.

This will give an error

make test TEST="micro:java.lang.StringConcat.concat6String" -Djava.lang.invoke.StringConcat.highArityThreshold=0

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/20273#discussion_r1692278005