RFR: 8317228: GC: Make TestXXXHeapSizeFlags use createTestJvm [v2]

[Leo Korinth]

On Fri, 13 Oct 2023 13:39:48 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

>> I agree it is a bit ugly and the point of this being an extension is good. An alternative would be to use `vm.xopt.Xmx` to even less clobber the `vm.opt` namespace, but I guess we already do by adding the `vm.opt.final` details. 
>> 
>> I'm ok with the current way, just wanted to raise possible alternatives.
>
> `vm.xopt` was my first choice, but it works badly because of other reasons, so lets keep it as it is now.

The reason is that we need to use a namespace that starts with `vm.opt`, because that string is *special* in JTREG. If the property starts with that prefix, there is no need to register all possible values manually --- something that would be hard to maintain. However, reusing parts of namespaces have prior art in for example `vm.gc.*` so although maybe not optimal, it should not be problematic. It follows standard practice.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15986#discussion_r1358301087