[crac] RFR: 8353241: [CRaC] Support ZGC [v3]

[Timofei Pushkin]

On Mon, 14 Apr 2025 07:16:53 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> src/hotspot/share/runtime/crac.cpp line 429:
>> 
>>> 427:     MemTracker::final_report(tty);
>>> 428:   }
>>> 429: 
>> 
>> Is this left intentionally? If yes, I think nothing will be printed after this on the real VM exit (after restore) since there is `Atomic::cmpxchg(&g_final_report_did_run, false, true) == false` in `MemTracker::final_report()`.
>
> Yes, I've left this intentionally. Well spotted, I'll make sure that the final report will run as well.

I actually think that this should be done in as a separate change then. I would propose to either document that `PrintNMTStatistics` prints on checkpoint, or make it have several modes (0 — off, 1 — print on exit, 2 — print on checkpoint, 4 — print on both exit and checkpoint), or add a separate `PrintNMTStatisticsOnCheckpoint`. The reason why I am proposing this is because I believe we had a related request from community for this somewhere, so it would be nice to have this documented.

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PR Review Comment: https://git.openjdk.org/crac/pull/219#discussion_r2041556788