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

[Aleksey Shipilev]

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?

Looks fine, a few nits.

test/hotspot/jtreg/containers/docker/TestMemoryInvisibleParent.java line 96:

> 94:         opts.addDockerOpts("--cgroup-parent=/" + cgroupParent);
> 95:         Common.run(opts)
> 96:             .shouldContain("Hierarchical Memory Limit is: " + expectedValue);

Indenting a a bit off here.

test/hotspot/jtreg/containers/docker/TestMemoryInvisibleParent.java line 107:

> 105:         Path sysFsMemory = Path.of("/", "sys", "fs", "cgroup", "memory");
> 106:         Path cgroupParentPath = sysFsMemory.resolve(cgroupParent);
> 107:         ProcessBuilder pb = new ProcessBuilder("mkdir", "-p", cgroupParentPath.toString());

So I am guessing we are fine with leaving this cgroup behind, after the test is done?

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Marked as reviewed by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28201#pullrequestreview-3441857489
PR Review Comment: https://git.openjdk.org/jdk/pull/28201#discussion_r2509492642
PR Review Comment: https://git.openjdk.org/jdk/pull/28201#discussion_r2509498605