RFR: 8356868: Not all cgroup parameters are made available [v2]

[Casper Norrbin]

On Fri, 20 Jun 2025 16:47:56 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>> Casper Norrbin has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   update cpu usage to use >=
>>   
>>   Co-authored-by: Severin Gehwolf <jerboaa at gmail.com>
>
> src/hotspot/os/linux/cgroupV1Subsystem_linux.cpp line 431:
> 
>> 429:   return (jlong)cpu_usage / 1000;
>> 430: }
>> 431: 
> 
> Why don't we report the original value in nanos, if it is available?
> 
> This is new API, so no-one is using this yet, right?

I centered it around cgroup v2, which only reports the usage in micros. Cgroup v1 is deprecated for most systems so shouldn't really be used. It made more sense to use micros instead of padding the value most will see with a bunch of zeros.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25388#discussion_r2161223525