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List:       openjdk-serviceability-dev
Subject:    Re: [PING] RFR: 8231111: Cgroups v2: Rework Metrics in java.base so as to recognize unified hierarch
From:       Bob Vandette <bob.vandette () oracle ! com>
Date:       2020-01-22 16:19:07
Message-ID: 80051010-726E-4349-9C65-4804A27E6F5E () oracle ! com
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> On Jan 22, 2020, at 11:06 AM, Mandy Chung <mandy.chung@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


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