RFR: 8344445: MethodCounters don't need a vptr [v2]

[Coleen Phillimore]

On Tue, 19 Nov 2024 08:07:39 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> src/hotspot/share/oops/methodCounters.hpp line 61:
>> 
>>> 59:   void deallocate_contents(ClassLoaderData* loader_data) {}
>>> 60: 
>>> 61:   void metaspace_pointers_do(MetaspaceClosure* it) { return; }
>> 
>> Does it change the behavior if we remove this along with
>> ` it->push(&_method_counters);`
>> in Method::metaspace_pointers_do?
>
> That would violate the contract for MetaspaceObj.
> https://github.com/openjdk/jdk/blob/499186be0fa70dba4b008cdafb72aba6addb2965/src/hotspot/share/memory/allocation.hpp#L247-L261

Yes it's a metaspace pointer.  It's zeroed and not saved in the archive but it still needs to call this function in case it's not zeroed and someday called.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22220#discussion_r1848250136