RFR: 8331560: Refactor Hotspot container detection code so that subsystem delegates to controllers [v3]

[Johan Sjölen]

On Wed, 29 May 2024 17:42:13 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Please review this preparatory PR which is an enabler for some bugfix/alignment work (e.g. [JDK-8322420](https://bugs.openjdk.org/browse/JDK-8322420)). The idea is to delegate limit lookup to controllers (`memory`, `cpu`, etc.) from the overarching `CgroupSubsystem` class. This way we can - once the cg type has been detected - "adjust" a controller's path to the limit files when the controller is being created (on init) and then left alone. In this case, the two preparatory entry points are `CgroupUtil::processor_count()` taking a version-agnostic `CgroupCpuController` to do the actual look-up and `CgroupMemoryController::read_memory_limit_in_bytes()` for the same in terms of memory limits.
>> 
>> This enables setting the contoller's path to the interface files (wherever it might be in the hierarchy of it's original cgroup path), look up the limit and "freeze" the path once it found a - lower - limit.
>> 
>> It also ensures that both cgroup versions return `-1` or `-2` (`OSCONTAINER_ERROR`) - in both cases negative - for some notion of unlimited. I.e. it makes the upper bound by the host's physical memory apparent in the version agnostic classes.
>> 
>> Testing:
>> - [x] GHA
>> - [x] gtest:cgroupTest tests
>> - [x] container tests on Linux cgv1 and cgv2 on x86_64
>> 
>> Thoughts?
>
> Severin Gehwolf has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 30 commits:
> 
>  - Review feedback
>  - Clean up
>  - Appropriately handle version specific printing
>  - Fix inheritance hierarchy
>  - Fixup after merge
>  - Merge branch 'master' into jdk-8331560-cgroup-controller-delegation
>  - Resolve ambiguity with static_cast
>  - Remove limit_from_str from util class
>  - Merge branch 'jdk-8302744-cleanup-getcontainer-info' into jdk-8331560-cgroup-controller-delegation
>  - Add proper comments for parsing utility functions
>  - ... and 20 more: https://git.openjdk.org/jdk/compare/9b64ece5...e177a086

This code has (in general, not just this PR) a lot of unnecessary complexity. We can easily shave that complexity down, there's a lot of low hanging fruit here it seems. I'm seriously wondering if maybe we should get to these easier parts before we do another refactoring.

src/hotspot/os/linux/cgroupV1Subsystem_linux.hpp line 69:

> 67:     jlong kernel_memory_limit_in_bytes(julong host_mem);
> 68:     jlong kernel_memory_max_usage_in_bytes();
> 69:     void print_version_specific_info(outputStream* st, julong host_mem);

Can you add `override` to the end of the virtual functions here? `jlong memory_usage_in_bytes() override;`, like so.

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PR Review: https://git.openjdk.org/jdk/pull/19085#pullrequestreview-2115389533
PR Review Comment: https://git.openjdk.org/jdk/pull/19085#discussion_r1637970245