RFR: JDK-8262068: Improve G1 Full GC by skipping compaction for regions with high survival ratio [v12]

[Thomas Schatzl]

On Tue, 30 Mar 2021 02:50:25 GMT, Hamlin Li <mli at openjdk.org> wrote:

> Thanks Thomas, sure, will hold until your test finished.
> At the same time, we are also run perf tests to make sure the good performance of this final version.

gc/g1/TestEagerReclaimHumongousRegionsClearMarkBits.java fails with a fairly unknown error every few runs with this change:

    [26.103s][info][gc,start] GC(112) Pause Full (G1 Evacuation Pause)
    # To suppress the following error report, specify this argument
    # after -XX: or in .hotspotrc:  SuppressErrorAt=/g1BlockOffsetTable.cpp:358
    #
    # A fatal error has been detected by the Java Runtime Environment:
    #
    #  Internal Error (.../src/hotspot/share/gc/g1/g1BlockOffsetTable.cpp:358), pid=74345, tid=74370
    #  guarantee(backskip <= max_backskip) failed: Going backwards beyond the start_card. start_card: 225280 current_card: 225281 backskip: 256

There is a strong likelihood that this is a pre-existing issue and not directly caused by this change. I will need to investigate this.

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