Jason Lowe commented on YARN-2440:

bq. Specifically in the context of heterogeneous clusters where uniform % 
configurations can go really bad where the only resort will then be to do 
per-node configuration - not ideal.

Yes, I could see the heterogenous cluster being a case where specifying 
absolute instead of relative may be desirable.  My biggest concern is that it's 
confusing when trying to combine the absolute and relative concepts -- it's not 
obvious if one overrides the other or if one is relative to the other.

Part of my concern to keep this as simple as possible and the configuration 
burden to an absolute minimum is that I'm missing the real-world use case.  As 
I mentioned before, I think most users would rather not use the functionality 
proposed by this JIRA but instead setup peer cgroups for other systems and set 
their relative cgroup shares appropriately.  With this JIRA the CPUs could sit 
idle despite demand from YARN containers, while a peer cgroup setup allows CPU 
guarantees without idle CPUs if the demand is there.

> Cgroups should allow YARN containers to be limited to allocated cores
> ---------------------------------------------------------------------
>                 Key: YARN-2440
>                 URL: https://issues.apache.org/jira/browse/YARN-2440
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Varun Vasudev
>            Assignee: Varun Vasudev
>         Attachments: apache-yarn-2440.0.patch, apache-yarn-2440.1.patch, 
> apache-yarn-2440.2.patch, apache-yarn-2440.3.patch, apache-yarn-2440.4.patch, 
> screenshot-current-implementation.jpg
> The current cgroups implementation does not limit YARN containers to the 
> cores allocated in yarn-site.xml.

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