G1 concurrent refinement regression

[Thomas Schatzl]

Hi Brian,

On 29.09.25 17:27, Brian S O'Neill wrote:
> Here's the timings under ideal conditions (no logging overhead, priority 
> boost):
> 
> Pre JEP 522 no conc refinement:    499 seconds
> Pre JEP 522 with conc refinement:  492 seconds
> Post JEP 522 no conc refinement:   488 seconds
> Post JEP 522 with conc refinement: 518 seconds
> 
> In my case it seems that with JEP 522, concurrent refinement should be 
> disabled to see any benefit.

Filed https://bugs.openjdk.org/browse/JDK-8368935.

It indeed seems like this is a stress test; from the attached logs 
(thanks) I can see that the test apparently over and over again marks 
(mostly) single cards in the card table by adding a reference and then 
clearing them (nulling) again.

G1's card marking activity monitoring just sees the constant re-marking 
indicated by the large mark rate. After refinement cleared all the 
cards, repeat.

There is basically no other activity.

We'll see if we can improve this kind of application. We were planning 
on decreasing refinement activity anyway.

Maybe, since it's a stress test, you can share it?

Thanks,
   Thomas