[PING] RFR: 8231111: Cgroups v2: Rework Metrics in java.base so as to recognize unified hierarchy

[Mandy Chung]

Hi Bob, Severin,

On 1/9/20 11:51 AM, Severin Gehwolf wrote:
> Thanks for the review! Should all be fixed now. Updated webrev:
>
> incremental:http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8231111/07/incremental/webrev/
> full:http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8231111/07/webrev/

This patch may be more appropriate to be reviewed by the serviceability 
group (cc'ed) as this is monitoring-related.

jdk.internal.platform.Metrics is an internal API that you are free to 
change the API as appropriate.  Given that 13 out of 38 metrics defined 
in Metrics are no longer supported by cgroups v2, it's cleaner to 
refactor Metrics interface to be implementable by cgroups v1 and v2 and 
then define a cgroups version-specific metrics to extend Metrics, which 
means that it seems reasonable to make it linux-only sub-interface.  
Client can cast to cgroup v1 metrics interface if needed.  Sorry for not 
chiming in earlier and I am not following the cgroups v2 changes.  This 
should be a straight-forward change which will make the implementation 
cleaner.  You would no longer need the new *_UNLIMITED and 
*_NOT_SUPPORTED constants.

A couple of quick comments when skimming on the new files:

CgroupSubsystemController.java
    s/parm/param (including javadoc @param tag)

CgroupInfo.java
    cgroupPath is not used??

Mandy