RFR: 8341643: G1: Merged cards counter skewed by merge cards cache [v2]

[Hamlin Li]

On Mon, 7 Oct 2024 14:53:11 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>    please review this change that subtracts the dummy cards from the merge cards counter at the end of the phase to keep its value correct.
>> 
>> E.g. previously log output with no actual cards being merged looks as follows:
>> 
>>  [0.991s][debug][gc,phases ] GC(11) Remembered Sets (ms): Min: 0.03, Avg: 0.03, Max: 0.03, Diff: 0.01, Sum: 0.11, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Eager Reclaim (ms): skipped
>> [0.991s][debug][gc,phases ] GC(11) Merged Inline: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged ArrayOfCards: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged Howl: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged Full: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged Howl Inline: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged Howl ArrayOfCards: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged Howl BitMap: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged Howl Full: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> [0.991s][debug][gc,phases ] GC(11) Merged Cards: Min: 8, Avg: 8.0, Max: 8, Diff: 0, Sum: 32, Workers: 4
>> 
>> (Note that none of the other categories have non-zero values)
>> to
>> 
>> [0.991s][debug][gc,phases ] GC(11) Merged Cards: Min: 0, Avg: 0.0, Max: 0, Diff: 0, Sum: 0, Workers: 4
>> 
>> 
>> For the same test (gcbasher in this case).
>> 
>> Testing: gha, log messages
>> 
>> Thanks,
>>   Thomas
>
> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
> 
>   * fix documentation

Marked as reviewed by mli (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/21390#pullrequestreview-2354067778