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

[Mandy Chung]

On 1/22/20 1:53 AM, Severin Gehwolf wrote:
> Hi Mandy,
>
> Thanks again for the review! I'll be sure to fix things. Some of the
> issues you've pointed out probably pre-existed in old code. Some became
> more complicated since unlimited in cgroupv1 is a large long value in
> files. Anyway, I'll update it.

Thank you.
> On Tue, 2020-01-21 at 16:09 -0800, Mandy Chung wrote:
>> MetricsCgroupV1 is linux-only.  It will fail the compilation when
>> building on non-linux.
> I don't think so. MetricsCgroupV1 is a new interface in shared code
> just like Metrics itself:
>   src/java.base/share/classes/jdk/internal/platform/MetricsCgroupV1.java

Ah, I mis-read that was placed under src/java.base/linux/classes. OK.
> I've put it there for the exact reason to NOT break compilation on non-
> Linux. We could call it ExtendedMetrics or something, though. Pondered
> that for a bit, but it wasn't important enough so I've kept it.
>> One option is to move this code to
>>     src/java.base/linux/share/sun/launcher/CgroupMetrics.java
> Not sure if that would help. MetricsCgropuV1 is being used in
> LauncherHelper.java which itself is available on all platforms, no?

-XshowSettings:system is a linux-only option.
>> Are they continued to be interesting metrics to be output from
>> -XshowSetting?  I wonder if they can simply be dropped from the output.
>> Bob will have an opinion.
> I think they are. At least it prints the same metrics as were printed
> before this patch on cgroupv1. What's the rationale of not printing
> them any longer? My premise was, they were useful before and they
> continue to be useful. For cgroupv2 they're not configurable so they're
> not printed (and not useful as they'd show up as N/A anyway).

Bob can advice on the usefulness of these metrics.    I have no 
objection to print them on cgroup v1.  On v2,  they are not shown (not 
even N/A, right?)

Mandy