RFR: 8370966: Create regression test for the hierarchical memory limit fix in JDK-8370572

[SendaoYan]

On Fri, 7 Nov 2025 16:41:26 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

> Please review this test-only enhancement. It creates a regression test for the Amazon ECS setup on cgroups v1 where the parent memory limit isn't visible inside the container and, thus, needs to rely on the cg v1 specific `hierarchical_memory_limit` token in `memory.stat`. The proposed test is cg v1 only and needs to be run as root. It's skipped otherwise. It's useful to have when working on refactorings like #27743  so as not to regress.
> 
> The other changes are an effort to reduce code duplication in the test code where similar patterns have been used in other container tests.
> 
> Testing (all on Linux x86_64):
> - [x] CG version 2, run as root. Engine: docker. Test is skipped.
> - [x] CG version 1, run as root. Engine: docker. Test passes and fails without the product fix of [JDK-8370572](https://bugs.openjdk.org/browse/JDK-8370572)
> - [x] CG version 1, run as root. Engine: podman. Test passes and fails without the product fix of [JDK-8370572](https://bugs.openjdk.org/browse/JDK-8370572)
> - [X] CG version 1, run as non-root. Test skipped.
> - [x] GHA, though I don't think this is very useful for this change.
> 
> Thoughts?

test/hotspot/jtreg/containers/docker/TestMemoryInvisibleParent.java line 2:

> 1: /*
> 2:  * Copyright (C) 2025, IBM

Copyright (c) 2025 IBM Corporation. All rights reserved.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28201#discussion_r2508961551