RFR: 8317371: GenShen: Needs improved support for humongous allocation [v3]

[Kelvin Nilsen]

On Thu, 12 Oct 2023 17:55:31 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Cosmetic improvements
>
> src/hotspot/share/gc/shenandoah/heuristics/shenandoahOldHeuristics.cpp line 572:
> 
>> 570: 
>> 571:     // New active regions may have came into play following the trigger.
>> 572:     size_t first_region = MIN2(first_active_region, first_old_region);
> 
> I don't understand this. The active region counts are not updated after the trigger?

I agree this is confusing.  I'm going to simplify this code and have the log message report the data that drove the trigger.  The reality is that between the moment in time that we raised the trigger (from inside ShenandoahHeap::rebuild_free_set(), and the moment that the regulator polls the old heuristic's state to discover that we should_start_gc(), the state may change so this log message may be slightly out of date.  This would be extremely unlikely.  The trigger happens at final-update-refs.  The old-gen state will not change until we begin a subsequent evacuation phase.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/336#discussion_r1357601310