Integrated: 8331560: Refactor Hotspot container detection code so that subsystem delegates to controllers

[Severin Gehwolf]

On Fri, 3 May 2024 12:24:02 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?

This pull request has now been integrated.

Changeset: 153b12b9
Author:    Severin Gehwolf <sgehwolf at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/153b12b9df87fdf8122cae3bf7f13078f55f7101
Stats:     592 lines in 8 files changed: 329 ins; 82 del; 181 mod

8331560: Refactor Hotspot container detection code so that subsystem delegates to controllers

Reviewed-by: jsjolen, stuefe

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PR: https://git.openjdk.org/jdk/pull/19085