RFR: 8256806: Shenandoah: optimize shenandoah/jni/TestPinnedGarbage.java test

[Roman Kennke]

On Fri, 20 Nov 2020 19:15:31 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This test is way too slow for Zero configuration, taking about 2 hours. No reasonable timeout factor accounts for this. We can clean the test up and make it more lenient. It would also improve server testing time.
> 
> Current proposal cuts down the test heap 4x, and thus the number of objects it needs to handle 4x as well. Additionally, moving `Random` initialization out of tested method marginally improves the times. I also went back to remember why this test even exists, and it has to do with [Full GC handling pinned objects specially](http://hg.openjdk.java.net/shenandoah/jdk8/hotspot/rev/bc0f0cfed315). I injected the bug back, and the test still caught it.
> 
> Additional testing:
>  - [x] Linux x86_64 Zero fastdebug, affected test
>  - [x] Linux x86_64 Server fastdebug, affected test
>  - [x] Linux x86_32 Server fastdebug, affected test

Looks good to me! Thank you!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1358