Integrated: 8285984: G1: Use standard idiom for inlined payload in G1MonotonicArena::Segment

[Leo Korinth]

On Fri, 12 Sep 2025 12:26:19 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

> This change remove the old padding (extremely big, especially on x86-64), and replaces it with a guaranteed 8 byte alignment. It also removes the `_bottom` field and instead adds a `payload` method. I statically assert that Segment is 8 byte aligned. I then runtime assert that Segment is constructed on 8 byte aligned memory. I also assert that the Slot alignment is less than or equal to the Segment alignment.
> 
> I am running tier 1-3 at the moment. Do you think I should run some specific performance test on this?

This pull request has now been integrated.

Changeset: bf726e82
Author:    Leo Korinth <lkorinth at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/bf726e821790fad6ee304c1c36bddedbfe4152ff
Stats:     15 lines in 3 files changed: 5 ins; 3 del; 7 mod

8285984: G1: Use standard idiom for inlined payload in G1MonotonicArena::Segment

Reviewed-by: aboldtch, tschatzl

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PR: https://git.openjdk.org/jdk/pull/27258