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

[Bob Vandette]

> On Jan 22, 2020, at 11:06 AM, Mandy Chung <mandy.chung at oracle.com> wrote:
> 
> 
> 
> 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?)

These metrics are not that useful in the -XshowSettings context.  I’d just drop them from the output.

Bob.


> 
> Mandy