[PING2!] RFR: 8230305: Cgroups v2: Container awareness

[Bob Vandette]

> On Jan 15, 2020, at 5:13 PM, David Holmes <david.holmes at oracle.com> wrote:
> 
> Hi Bob, Severin,
> 
> On 15/01/2020 6:04 am, Bob Vandette wrote:
>> Cgroup V2 is about to go mainstream this year for popular distros such as Oracle Linux 8, Redhat Linux 8 and Fedora
>> so this fix it’s important to get into JDK 15 so we can start shaking out this support.
>> Please take a look and help get this change reviewed.
> 
> I've taken a look and the overall structure and approach seems fine. I can't attest to the details of cgroups v1 versus v2 but trust the exports.
> 
> Reviewed.
> 
> Please ensure all copyrights updated to 2020.
> 
> Bob: I assume you have tested this on our systems?

I’m in the process of setting up a cgroup v2 system to test with but I’ll grab the patch and verify the
container tests on my cgroup v1 setup today.

Bob.


> 
> Thanks,
> David
> 
>> Thanks,
>> Bob Vandette
>>> On Nov 29, 2019, at 4:04 AM, Severin Gehwolf <sgehwolf at redhat.com> wrote:
>>> 
>>> On Fri, 2019-11-15 at 17:56 +0100, Severin Gehwolf wrote:
>>>> On Fri, 2019-11-08 at 15:21 +0100, Severin Gehwolf wrote:
>>>>> Hi Bob,
>>>>> 
>>>>> On Wed, 2019-11-06 at 10:47 +0100, Severin Gehwolf wrote:
>>>>>> On Tue, 2019-11-05 at 16:54 -0500, Bob Vandette wrote:
>>>>>>> Severin,
>>>>>>> 
>>>>>>> Thanks for taking on this cgroup v2 improvement.
>>>>>>> 
>>>>>>> In general I like the implementation and the refactoring.  The CachedMetric class is nice.
>>>>>>> We can add any metric we want to cache in a more general way.
>>>>>>> 
>>>>>>> Is this the latest version of the webrev?
>>>>>>> 
>>>>>>> http://cr.openjdk.java.net/~sgehwolf/webrevs/cgroupsv2-hotspot/03/webrev/src/hotspot/os/linux/cgroupV2Subsystem_linux.cpp.html
>>>>>>> 
>>>>>>> It looks like you need to add the caching support for active_processor_count (JDK-8227006).
>>>>> [...]
>>>>>> I'll do a proper rebase ASAP.
>>>>> 
>>>>> Latest webrev:
>>>>> http://cr.openjdk.java.net/~sgehwolf/webrevs/cgroupsv2-hotspot/05/webrev/
>>>>> 
>>>>>>> I’m not sure it’s worth providing different strings for Unlimited versus Max or Scaled shares.
>>>>>>> I’d just try to be compatible with the cgroupv2 output so you don’t have to change the test.
>>>>>> 
>>>>>> OK. Will do.
>>>>> 
>>>>> Unfortunately, there is no way of NOT changing TestCPUAwareness.java as
>>>>> it expects CPU Shares to be written to the cgroup filesystem verbatim.
>>>>> That's no longer the case for cgroups v2 (at least for crun). Either
>>>>> way, most test changes are gone now.
>>>>> 
>>>>>>> I wonder if it’s worth trying to synthesize memory_max_usage_in_bytes() by keeping the highest
>>>>>>> value ever returned by the API.
>>>>>> 
>>>>>> Interesting idea. I'll ponder this a bit and get back to you.
>>>>> 
>>>>> This has been implemented. I'm not sure this is correct, though. It
>>>>> merely piggy-backs on calls to memory_usage_in_bytes() and keeps the
>>>>> high watermark value of that.
>>>>> 
>>>>> Testing passed on F31 with cgroups v2 controllers properly configured
>>>>> (podman) and hybrid (legacy hierarchy) with docker/podman.
>>>>> 
>>>>> Thoughts?
>>>> 
>>>> Ping?
>>> 
>>> Anyone willing to review this? It would be nice to make some progress.
>>> 
>>> Thanks,
>>> Severin
>>> 
>>>> Metrics work proposed for RFR here:
>>>> http://mail.openjdk.java.net/pipermail/core-libs-dev/2019-November/063464.html
>>>> 
>>>> Thanks,
>>>> Severin
>>>