RFR: 8349146: [REDO] Implement a better allocator for downcalls [v6]

[Maurizio Cimadamore]

On Wed, 30 Apr 2025 15:33:52 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR is based on the work of @mernst-github and aims to implement an _internal_ thread-local 'stack' allocator, which works like a dynamically sized arena, but with reset functionality to reset the allocated size back to a certain level. The underlying memory could stay around between calls, which could improve performance.
>> 
>> Re-allocated segments are not zeroed between allocations.
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Improve on comments

src/java.base/share/classes/jdk/internal/foreign/BufferStack.java line 81:

> 79:     @Override
> 80:     public int hashCode() {
> 81:         return System.identityHashCode(this);

What's the value in these overloads? Isn't this implementation the same we'd get if there were no overrides?

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PR Review Comment: https://git.openjdk.org/jdk/pull/24829#discussion_r2070015191