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

[Kelvin Nilsen]

On Thu, 12 Oct 2023 17:51:23 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 562:
> 
>> 560:     size_t first_active_region = heap->free_set()->first_old_region();
>> 561:     size_t last_active_region = heap->free_set()->last_old_region();
>> 562:     size_t span_of_active_regions = (last_active_region > first_active_region)? last_active_region + 1 - first_active_region: 0;
> 
> Why did we compute `span_of_active_regions`? Doesn't seem used. If we don't need `span_of_active_regions`, do we still need the new methods: `first_old_region` and `last_old_region`?

Thanks for this catch also.  I went through a few iterations of how to implement this, and forgot to clean up all of my experiments.  Am removing this code and am removing first_old_region() and last_old_region().  We only "need" the first and last old region info immediately after we rebuild the Shenandoah Free Set.  Since the rebuild process already iterates over all regions, it's best to compute the information during that pass.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/336#discussion_r1357584893