RFR: 8244847: Linux/PPC: runtime/CompressedOops/CompressedClassPointers: smallHeapTest fails [v2]

[Richard Reingruber]

On Mon, 30 Nov 2020 11:00:21 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> 
> 
> Thanks for fixing it! Looks good to me, too. Was it tested on AIX?

Yes, it was tested on AIX. I've overlooked a failure though, sorry...

The test CompressedClassPointers.largeHeapTest() fails on AIX because it manages to get a zerobased CCS which is unexpected. Actually a zerobased CCS is good but we get it accidentally because the first attempt to place it behind the heap which is located above 32g fails. On Linux/PPC this test succeeds because this first attempt to allocate a high CCS succeeds which is actually not optimal.

For now I excluded the narrow klass base test on AIX (as it was before).

As an enhancement the first attempt to reserve address space for CCS should be below 32g if the coops heap was placed above 32g. I will open a JBS item for this.

Thanks for the review. I will report back on the test results.

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PR: https://git.openjdk.java.net/jdk/pull/1512