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[placement][nova][ptg] resource provider affinity


Contribute an another idea at here. Pretty sure I didn't explore this with
all the cases by my limited vision.

So I'm thinking we can continue use query string build a tree structure by
the request group number. I know the number request group problem for the
cyborg and neutron, but I think there must be some way to describe the
cyborg device will be attached to which instance numa node. So I guess that
it isn't the fault of number request group, maybe we are just missing a way
to describe that.

For the case in the spec https://review.openstack.org/#/c/650476, an
instance with one numa node and two VFs from different network. We can
write as below:

?resources=DISK_GB:10&
resources1=VCPU:2,MEMORY_MB:128&
resources1.1=VF:1&required=NET_A
resources1.2=VF:1&required=NET_B

Another example, we request an instance with two numa nodes, 2 vcpus and
128mb memory in each node. In each node has two VFs come from different PF
to have HA.

?resources=DISK_GB:10&
resources1=VCPU:2,MEMORY_MB:128&
resources1.1=VF:1&
resources1.2=VF:1&
resources2=VCPU:2,MEMORY_MB:128&
resources2.1=VF:1&
resources2.2=VF:1&
group_policy=isolate&
group_policy1=isolate&
group_policy2=isolate

The `group_policy` ensure the resources1 and resources2 aren't coming from
the same RP. The 'group_poilcy1' ensures `resource1.x` aren't coming from
the same RP. The `group_policy2` ensures `resources2.x` aren't coming from
same RP.

For the cyborg case, I think we can propose the flavor extra specs as below:
accel:device_profile.[numa node id]=<profile_name>

Then we will know the user hope the cyborg device being attach to which
instance numa node.

The cyborg only needs to return un-numbered request group, then Nova will
base on all the 'hw:xxx' extra specs and 'accel:device_profile.[numa node
id]' to generate a placement request like above.

For example, if it is PCI device under first numa node, the extra spec will
be 'accel:device_profile.0=<profile_name>' the cyborg can return a simple
request 'resources=CYBORG_PCI_XX_DEVICE:1', then we merge this into the
request group 'resources1=VCPU:2,MEMORY_MB:128,CYBORG_PCI_XX_DEVICE:1'. If
the pci device has a special trait, then cyborg should return request group
as 'resources1=CYBORG_PCI_XX_DEVICE:1&required=SOME_TRAIT', then nova merge
this into placement request as 'resources1.1'.

Chris Dent <cdent+os at anticdent.org> äº?2019å¹´4æ??9æ?¥å?¨äº? ä¸?å??8:42å??é??ï¼?

>
> Spec: https://review.openstack.org/650476
>
> From the commit message:
>
>      To support NUMA and similar concepts, this proposes the ability
>      to request resources from different providers nested under a
>      common subtree (below the root provider).
>
> There's much in the feature described by the spec and the surrounding
> context that is frequently a source of contention in the placement
> group, so working through this spec is probably going to require
> some robust discussion. Doing most of that before the PTG will help
> make sure we're not going in circles in person.k
>
> Some of the areas of potential contention:
>
> * Adequate for limited but maybe not all use case solutions
> * Strict trait constructionism
> * Evolving the complexity of placement solely for the satisfaction
>    of hardware representation in Nova
> * Inventory-less resource providers
> * Developing new features in placement before existing features are
>    fully used in client services
> * Others?
>
> I list this not because they are deal breakers or the only thing
> that matters, but because they have presented stumbling blocks in
> the past and we may as well work to address them (or make an
> agreement to punt them until later) otherwise there will be
> lingering dread.
>
> And, beyond all that squishy stuff, there is the necessary
> discussion over the solution described in the spec. There are
> several alternatives listed in the spec, and a few more in the
> comments. We'd like to figure out the best solution that can
> actually be done in a reasonable amount of time, not the best
> solution in the absolute.
>
> Discuss!
>
> --
> Chris Dent                       Ù©â??̯â??Û¶           https://anticdent.org/
> freenode: cdent                                         tw: @anticdent
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