RFR: 8148745: [testbug] Test gc/g1/plab/TestPLABPromotion.java fails in nightly

[Michail Chernov]

Hi Thomas,

Thanks for review.
> Since -Xcomp does not seem to add any new information to the test,
> couldn't it simply be disallowed to use with this test instead?
I agree, it does not add new cases for GC testing, but adding of -Xcomp 
for testing sounds reasonable for compiler part.
For SQE part, I'd like to keep more possible VM options combinations.
>
> The 01 version looks okay. I assume proper testing with this change has
> been performed (running it through our test systems a few times).
Yes, the change was tested on all platforms with all possible nightly 
options combinations.

Thanks
Michail