RFR: 8253815: Remove unused HeapRegionManager::_num_committed from SA

[Chris Plummer]

On Tue, 29 Sep 2020 21:28:07 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

>> src/hotspot/share/gc/g1/vmStructs_g1.hpp line 56:
>> 
>>> 54:                                                                               \
>>> 55:   nonstatic_field(HeapRegionManager, _regions,          G1HeapRegionTable)    \
>>> 56:   nonstatic_field(HeapRegionManager, _num_committed,    uint)                 \
>> 
>> If this field is remaining in hotspot, it should also remain in vmStructs. Although SA does not need to explicitly know
>> about this field to function properly, SA can be used to dump hotspot objects, and can only dump objects whose types
>> are in vmStructs, and for those types can only display the fields that are also in vmStructs.
>
> The field will remain for now, but the plan is to refactor it into a new class. The new class is not needed by the SA
> and I would really like to avoid having to add unused and untested code to the SA. To simplify this coming change I
> want to remove this from the SA straight away.   Even without this coming change I would vote for removing this type of
> unused code from the SA. I don't think being able to dump the value is worth enough compared to the maintenance cost of
> keeping it in.

Ok. If the field is going away eventually then you can remove it now.

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PR: https://git.openjdk.java.net/jdk/pull/408