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https://issues.apache.org/jira/browse/YARN-1024?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13766124#comment-13766124
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Eli Collins commented on YARN-1024:
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bq. keeping virtual cores to express parallelism sounds good as it is clear it
is not a real core.
Hm, I read this the other way. If a framework asks for three vcores on a host
it intends to run some code on three real physical cores at the same time. If a
long lived framework wants to reserve 2 cores per host it would ask for 2 cores
(and 100% YCU per core).
Sandy's proposal, switching to cores and YCU instead of just vcores, is
equivalent to the proposal above of getting rid of vcores and supporting
fractional cores. A vcore becomes a "core" and YCU is just a way to express
that you want a fraction of a core. Sounds good to me.
> Define a virtual core unambigiously
> -----------------------------------
>
> Key: YARN-1024
> URL: https://issues.apache.org/jira/browse/YARN-1024
> Project: Hadoop YARN
> Issue Type: Improvement
> Reporter: Arun C Murthy
> Assignee: Arun C Murthy
> Attachments: CPUasaYARNresource.pdf
>
>
> We need to clearly define the meaning of a virtual core unambiguously so that
> it's easy to migrate applications between clusters.
> For e.g. here is Amazon EC2 definition of ECU:
> http://aws.amazon.com/ec2/faqs/#What_is_an_EC2_Compute_Unit_and_why_did_you_introduce_it
> Essentially we need to clearly define a YARN Virtual Core (YVC).
> Equivalently, we can use ECU itself: *One EC2 Compute Unit provides the
> equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor.*
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