RFR: 8319161: GC: Make TestParallelGCThreads use createTestJavaProcessBuilder

[Stefan Karlsson]

On Sat, 29 Nov 2025 12:40:39 GMT, Ramkumar Sunderbabu <rsunderbabu at openjdk.org> wrote:

> Summary of change:
> 
> 1. executeLimitedTestJava changed to executeTestJava to allow flags to be propagated to forked processes.
> 2. `@requires vm.gc == null` - this line is added to skip runs that use GC flags in test vm options. Allowing GC flags will result in VM initialization error ("Multiple garbage collectors selected").
> 3. Addition of ZGC to list of parallel collectors
> 
> Testing:
> HS Tiers 1 and 2
> Ran with all flag combinations in CI

Could we instead run with explicit test sections that list all supported GCs, similarly to what we do in `test/hotspot/jtreg/gc/TestSystemGC.java`. That way we our CI tasks that run with a specified GC also runs this test.

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

PR Comment: https://git.openjdk.org/jdk/pull/28566#issuecomment-3595583088