RFR: 8197589: CPU count wrong when both cpu shares and quotas are used

[David Holmes]

Hi Bob,

On 13/02/2018 5:53 AM, Bob Vandette wrote:
> Updated webrev URL.
> 
> 
>> On Feb 12, 2018, at 2:41 PM, Bob Vandette <bob.vandette at oracle.com> wrote:
>>
>> Please review this change to the cpu count selection logic used when running in docker containers.
>>
>> BUG:
>>
>> https://bugs.openjdk.java.net/browse/JDK-8197589
>>
>> WEBREV:
>>
>> http://cr.openjdk.java.net/~bobv/8197589/webrev.00/
>>
>> The algorithm implemented in JDK-8146115 for selecting the number of active cpus assumed that a container
>> would not be configured to use both cpu shares AND cpu quotas at the same time. This was an invalid assumption
>> since this how containers are configured to allow bursting activity [1].  A Java process running in a container with
>> cpu shares set to the equivalent of 2 cpus and a quota set to 6, will end up configuring the VM for 2 CPUs rather
>> than 6.
>>
>> [1] https://kubernetes.io/docs/tasks/configure-pod-container/assign-cpu-resource/#motivation-for-cpu-requests-and-limits

This really makes very little sense to me. They seem to be confusing 
utilization with number of physical processors that are available to 
use. The end result seems somewhat random to me. The number of threads 
the VM creates in response to the expected number of CPUs it has 
available is only indirectly related to the load those threads may then 
impose on the system. But I would have thought you would try to size the 
VM's use of threads based on the "request" not the "limit".

David

>>
>> Bob.
>>
>>
>