RFR: JDK-8297796 GenShen: instrument the remembered set scan [v12]

[William Kemper]

On Wed, 21 Dec 2022 17:43:55 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> I updated the summary comment at the top of the PR at https://github.com/openjdk/shenandoah/pull/176#issue-1471869802 with the new format based on Kelvin's suggestion in https://github.com/openjdk/shenandoah/pull/176#issuecomment-1342840919 above. It shows that the per round stats, separated by worker and scan type (UR or RS) is needed, and that the cumulative stats may have lost some of the nuance present in the per round/per scan type stats.
>
> Please let me know if there is still any confusion wrt the documentation of `ShenandoahCardStatsLogInterval` or if you'd prefer a rewording. Thanks!

Maybe "Log cumulative card stats every so many scans of the remembered set"? "Cycle" is a bit overloaded. If I read this, I would expect to see a log message every 50 GC cycles, but with (probably) two rset scans per GC cycle, it would be closer to every 25 GC cycles.

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PR: https://git.openjdk.org/shenandoah/pull/176