[openstack-dev] [Cyborg] [Nova] Backup plan without nested RPs

Stephen Finucane sfinucan at redhat.com
Tue Jun 5 12:50:52 UTC 2018


On Mon, 2018-06-04 at 10:49 -0700, Nadathur, Sundar wrote:
>     Hi,
> 
>          Cyborg needs to create RCs and traits for accelerators. The
>     original plan was to do that with nested RPs. To avoid rushing
> the
>     Nova developers, I had proposed that Cyborg could start by
> applying
>     the traits to the compute node RP, and accept the resulting
> caveats
>     for Rocky, till we get nested RP support. That proposal did not
> find
>     many takers, and Cyborg has essentially been in waiting mode.
> 
>     
> 
>     Since it is June already, and there is a risk of not delivering
>     anything meaningful in Rocky, I am reviving my older proposal,
> which
>     is summarized as below:
> 
>     
>       Cyborg shall create the RCs and traits as per spec
>         (https://review.openstack.org/#/c/554717/), both in Rocky and
>         beyond. Only the RPs will change post-Rocky.
> 
>       
>       In Rocky:
>       
>         Cyborg will not create nested RPs. It shall apply the device
>           traits to the compute node RP.
>         Cyborg will document the resulting caveat, i.e., all devices
>           in the same host should have the same traits. In
> particular,
>           we cannot have a GPU and a FPGA, or 2 FPGAs of different
>           types, in the same host.
>         Cyborg will document that upgrades to post-Rocky releases
>           will require operator intervention (as described below).
> 
>         
>       
>        For upgrade to post-Rocky world with nested RPs:
>       
>         The operator needs to stop all running instances that use an
>           accelerator.
>         The operator needs to run a script that removes the Cyborg
>           traits and the inventory for Cyborg RCs from compute node
> RPs.
>         The operator can then perform the upgrade. The new Cyborg
>           agent/driver(s) shall created nested RPs and publish
>           inventory/traits as specified.
>       
>     
>     IMHO, it is acceptable for Cyborg to do this because it is new
>       and we can set expectations for the (lack of) upgrade plan. The
>       alternative is that potentially no meaningful use cases get
>       addressed in Rocky for Cyborg. 
> 
>     
> 
>     Please LMK what you think.

I thought nested resource providers were already supported by
placement? To the best of my knowledge, what is not supported is virt
drivers using these to report NUMA topologies but I doubt that affects
you. The placement guys will need to weigh in on this as I could be
missing something but it sounds like you can start using this
functionality right now.

Stephen

>     
> 
>     Regards,
> 
>     Sundar
> 
>   
> 
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