RFR: 8343789: Move mutable nmethod data out of CodeCache [v9]

[Vladimir Kozlov]

On Thu, 21 Nov 2024 14:12:23 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

>> src/hotspot/share/code/codeBlob.hpp line 129:
>> 
>>> 127:   address _mutable_data;
>>> 128:   int     _mutable_data_size;
>>> 129: 
>> 
>> Should we add special CodeBlob subclass for nmethod to avoid increase of size for all blobs and stubs?
>
> I am not sure. All CodeBlobs with relocation info needs a mutable data. Let me know if you think it must be a separate subclass.

Please, move `_mutable_data` after `_oop_maps` and `_mutable_data_size` after `_size` to avoid padding.

Also update comment at line 70 to describe new CodeBlob layout.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21276#discussion_r1951678096