RFR: 8295267: Improve G1 scan to merge ratio calculation [v2]

[Ivan Walulya]

On Thu, 13 Oct 2022 13:56:32 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   can I have reviews for this change that fixes the merge-to-scan ratio calculation ("which fraction of the remembered sets creates unique cards") for predictions to make it more accurate and understandable?
>> 
>> Previously the denominator has been the total number of scanned cards; this seems to be a good approximation (trying to make a case for it, it's wrong) if the number of log buffers is low at GC start, but tends to get broken otherwise (i.e. with [JDK-8137022](https://bugs.openjdk.org/browse/JDK-8137022)).
>> 
>> This change fixes this to use the number of cards that were merged in.
>> 
>> This change depends on PR#10656. Please review that one first if not done otherwise.
>> 
>> Testing: tier1, checking that no tests use the "Dirty Cards" string now changed.
>> 
>> Thanks,
>>   Thomas
>
> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
> 
>   ayang review, merge_to_scan_ratio -> scan_to_merge_ratio

Marked as reviewed by iwalulya (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/10694