RFR: 8331087: Move immutable nmethod data from CodeCache [v2]

[Tobias Hartmann]

On Sun, 28 Apr 2024 23:37:22 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Move immutable nmethod's data from CodeCache to C heap. It includes `dependencies, nul_chk_table, handler_table, scopes_pcs, scopes_data, speculations`. It amounts for about 30% (optimized VM) of space in CodeCache.
>> 
>> Use HotSpot's `os::malloc()` to allocate memory in C heap for immutable nmethod's data. Call `vm_exit_out_of_memory()` if allocation failed.
>> 
>> Shuffle fields order and change some fields size from 4 to 2 bytes to avoid nmethod's header size increase.
>> 
>> Tested tier1-5, stress,xcomp
>> 
>> Our performance testing does not show difference.
>> 
>> Example of updated `-XX:+PrintNMethodStatistics` output is in JBS comment.
>
> Vladimir Kozlov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address comments. Moved jvmci_data back to mutable data section.

Looks good to me. Did you measure any impact on performance (potentially due to improved code density)?

What's left for [JDK-7072317](https://bugs.openjdk.org/browse/JDK-7072317)?

I wonder if the `CHECKED_CAST` changes shouldn't go into a separate RFE.

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Marked as reviewed by thartmann (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18984#pullrequestreview-2027660174