[PATCH] JDK-23: Fix for relocation set selecting in ZGC

[yifan zhang]

Hi ZGC Developers,

I've encountered an issue where ZGC might fail to promote objects
under a specific condition, leading to a memory leak. This patch aims
to fix it.

* Problem:
  The number of selected pages in the ZGC log is incorrect.

* Fix:
  The root cause lies in the execution of function
ZRelocationSetSelectorGroup::select_inner, where the count of selected
pages only includes the pages that satisfy the condition
diff_reclaimable > _fragmentation_limit, while ignoring the previously
accumulated pages.

  This results in a mismatch between the number of pages actually
reclaimed during relocation and the count reflected in the log.

  I have attached my modifications in the attachment.

* Testing:
  I've tested this fix by jtreg.

I would like to ask ZGC developers to review whether this can be
created as an issue. Once it is created, how should I commit my
modifications for it? Furthermore, how can I become an OpenJDK author?
Please help to review this patch. Any feedback is appreciated.

Thanks,
Yifan Zhang
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