RFR: 8343345: Use -jvmArgsPrepend when running microbenchmarks in RunTests.gmk

[Claes Redestad]

On Thu, 31 Oct 2024 12:12:21 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> Update RunTests.gmk to use `-jvmArgsPrepend` to avoid overwriting built-in micro `jvmArgs` flags.
>
> I had hoped you'd exclaim "Trivial!" and review, but I'm sure someone will step up soon enough. :-)

> @cl4es so what happens if someone now explicitly sets prepend args in the benchmark?

You mean if you do `@Fork(jvmArgsPrepend=...)`? Those will be overridden/ignored. The status before this and the related PR was that there was a mix of all the three variants in the OpenJDK JMH corpus, which complicated test setup. Microbenchmarks that explicitly defined `jvmArgs` would have had their VM settings ignored. 

Going forward we will try to make sure all micros use the `@Fork(jvmArgs=..)` option and nothing else to ensure flags have intended effect.

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PR Comment: https://git.openjdk.org/jdk/pull/21800#issuecomment-2450053412