RFR: JDK-8262068: Improve G1 Full GC by skipping compaction for regions with high survival ratio

[Stefan Johansson]

On Fri, 5 Mar 2021 02:57:11 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Hi Stefan , Thanks a lot for detailed review and benchmark!
>> Sure, I will update the patch as you suggested later.
>
> Hi Stefan,
> 
> There is jdk/tier1 test failure on MaxOS, it passed on other platforms: https://github.com/openjdk/jdk/pull/2760/checks?check_run_id=2033359984. 
> Rerun passed: https://github.com/Hamlin-Li/jdk/actions/runs/622899539

Even if the re-run passes this seems to be a real problem, probably just a bit intermittent. Looking at the test output you can see there is a segmentation fault in:
`G1FullGCPrepareTask::G1CalculatePointersClosure::prepare_for_skipping_compaction(...)`

Running the test with debug builds might make the issue reproduce on more platforms and give hints on what the problem is.

Hope this helps,
Stefan

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PR: https://git.openjdk.java.net/jdk/pull/2760