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

[Severin Gehwolf]

On Mon, 10 Nov 2025 09:23:36 GMT, Aleksey Shipilev <shade 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 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?

Yes. Unfortunately it's not easy to remove that. However, the test itself resets it to "unlimited" by setting the limit to `-1`. So it shouldn't make a difference.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28201#discussion_r2509510367