RFR: 8333446: Add tests for hierarchical container support [v6]

[Matthias Baesken]

On Wed, 28 Aug 2024 16:13:07 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Please review this PR which adds test support for systemd slices so that bugs like [JDK-8217338](https://bugs.openjdk.org/browse/JDK-8217338) can be verified. The added test, `SystemdMemoryAwarenessTest` currently passes on cgroups v1 and fails on cgroups v2 due to the way how [JDK-8217338](https://bugs.openjdk.org/browse/JDK-8217338) was implemented when JDK 13 was a thing. Therefore immediately problem-listed. It should get unlisted once [JDK-8322420](https://bugs.openjdk.org/browse/JDK-8322420) merges.
>> 
>> I'm adding those tests in order to not regress another time.
>> 
>> Testing:
>> - [x] Container tests on Linux x86_64 cgroups v2 and Linux x86_64 cgroups v1.
>> - [x] New systemd test on cg v1 (passes). Fails on cg v2 (due to  JDK-8322420)
>> - [x] GHA
>
> Severin Gehwolf has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:
> 
>  - Add root check for SystemdMemoryAwarenessTest.java
>  - Merge branch 'master' into jdk-8333446-systemd-slice-tests
>  - Merge branch 'master' into jdk-8333446-systemd-slice-tests
>  - Merge branch 'master' into jdk-8333446-systemd-slice-tests
>  - Add Whitebox check for host cpu
>  - Merge branch 'master' into jdk-8333446-systemd-slice-tests
>  - Merge branch 'master' into jdk-8333446-systemd-slice-tests
>  - Merge branch 'master' into jdk-8333446-systemd-slice-tests
>  - Fix comments
>  - 8333446: Add tests for hierarchical container support

src/hotspot/share/prims/whitebox.cpp line 2507:

> 2505: WB_END
> 2506: 
> 2507: // Physical cpus of the host machine (including containers), Linux only.

Isn't the comment a bit misleading ?  From what I see , ` os::Linux::active_processor_count()` can use various mechanisms to get number of processor info, if it uses https://linux.die.net/man/2/sched_getaffinity it gives the 'set of CPUs on which it is eligible to run.'   That might be different from what the host has.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19530#discussion_r1738427318