Integrated: 8349146: [REDO] Implement a better allocator for downcalls

[Per Minborg]

On Wed, 23 Apr 2025 14:05:58 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.

This pull request has now been integrated.

Changeset: 9f9e73d5
Author:    Per Minborg <pminborg at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/9f9e73d5f9fcb5e926a2674c54cbbc92012b75f6
Stats:     1004 lines in 11 files changed: 983 ins; 15 del; 6 mod

8349146: [REDO] Implement a better allocator for downcalls

Reviewed-by: mcimadamore, jvernee, liach

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PR: https://git.openjdk.org/jdk/pull/24829