RFR: 8302744: Refactor Hotspot container detection code [v2]

[Jan Kratochvil]

On Tue, 21 May 2024 13:58:22 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Please review this container detection code refactoring in hotspot. The main point of this is to
>> 
>> - get rid of the `GET_CONTAINER_INFO` macros which hide too many things under the hood
>> - prevent refactoring of the code (since `GET_CONTAINER_INFO` macros short-return and are therefore not portable; at least not without some risk)
>> - make the code easier to understand
>> - allow for better testing via `gtest`
>> - separate multi-line parsing from single line parsing for clarity.
>> 
>> Testing:
>> - [x] GHA
>> - [x] `gtest:cgroupTest` tests
>> - [x] Container tests on Linux with cgroup v1 (legacy) and cgroup v2. All pass.
>> 
>> Thoughts?
>
> 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 ten additional commits since the last revision:
> 
>  - Fix TestMemoryAwareness for cgroup v2
>    
>    It only reads the swap value, thus doesn't print:
>    "Memory and Swap Limit is" but rather prints:
>    "Swap Limit is". This is fine, since for cg v2
>    the memory limit and the swap limits are in different
>    files.
>  - Fix whitespace
>  - Handle cpu quota for cgroups v1 specially
>  - Try a different approach.
>    
>    Hybrid MACRO usage and locked down reading primitives.
>  - Add key-value read function
>  - Add basic testing for read functions
>  - Add generic julong/char* read functions
>  - Merge branch 'master' into jdk-8302744-cleanup-getcontainer-info
>  - 8302744: Refactor Hotspot container detection code

src/hotspot/os/linux/cgroupSubsystem_linux.cpp line 706:

> 704:   } else {
> 705:     log_debug(os, container)("Type %s not found in file %s", scan_fmt, absolute_path);
> 706:   }

Suggestion:

  }
  log_debug(os, container)("Type %s not found in file %s", scan_fmt, absolute_path);

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PR Review Comment: https://git.openjdk.org/jdk/pull/19060#discussion_r1609183562