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On Tue, May 29, 2018 at 11:52 AM, Sylvain Bauza 
<sylvain.bauza at gmail.com> wrote:
> 
> 
> 2018-05-29 11:01 GMT+02:00 Balázs Gibizer 
> <balazs.gibizer at ericsson.com>:
>> 
>> 
>> On Tue, May 29, 2018 at 9:38 AM, Sylvain Bauza <sbauza at redhat.com> 
>> wrote:
>>> 
>>> 
>>> On Tue, May 29, 2018 at 3:08 AM, TETSURO NAKAMURA 
>>> <nakamura.tetsuro at lab.ntt.co.jp> wrote
>>> 
>>>> > In that situation, say for example with VGPU inventories, that 
>>>> would mean
>>>> > that the compute node would stop reporting inventories for its 
>>>> root RP, but
>>>> > would rather report inventories for at least one single child RP.
>>>> > In that model, do we reconcile the allocations that were already 
>>>> made
>>>> > against the "root RP" inventory ?
>>>> 
>>>> It would be nice to see Eric and Jay comment on this,
>>>> but if I'm not mistaken, when the virt driver stops reporting 
>>>> inventories for its root RP, placement would try to delete that 
>>>> inventory inside and raise InventoryInUse exception if any 
>>>> allocations still exist on that resource.
>>>> 
>>>> ```
>>>> update_from_provider_tree() (nova/compute/resource_tracker.py)
>>>>   + _set_inventory_for_provider() (nova/scheduler/client/report.py)
>>>>       + put() - PUT /resource_providers/<rp_uuid>/inventories with 
>>>> new inventories (scheduler/client/report.py)
>>>>           + set_inventories() (placement/handler/inventory.py)
>>>>               + _set_inventory() 
>>>> (placement/objects/resource_proveider.py)
>>>>                   + _delete_inventory_from_provider() 
>>>> (placement/objects/resource_proveider.py)
>>>>                       -> raise exception.InventoryInUse
>>>> ```
>>>> 
>>>> So we need some trick something like deleting VGPU allocations 
>>>> before upgrading and set the allocation again for the created new 
>>>> child after upgrading?
>>>> 
>>> 
>>> I wonder if we should keep the existing inventory in the root RP, 
>>> and somehow just reserve the left resources (so Placement wouldn't 
>>> pass that root RP for queries, but would still have allocations). 
>>> But then, where and how to do this ? By the resource tracker ?
>>> 
>> 
>> AFAIK it is the virt driver that decides to model the VGU resource 
>> at a different place in the RP tree so I think it is the 
>> responsibility of the same virt driver to move any existing 
>> allocation from the old place to the new place during this change.
>> 
> 
> No. Allocations are done by the scheduler or by the conductor. Virt 
> drivers only provide inventories.

I understand that the allocation is made by the scheduler and the 
conductor but today the scheduler and the conductor do not have to know 
the structure for the RP tree to make such allocations. Therefore for 
me the scheduler and the conductor is a bad place to try to move 
allocation around due to a change in the modelling of the resources in 
the RP tree. In the other hand the virt driver knows the structure of 
the RP tree so it has the necessary information to move the existing 
allocaiton from the old place to the new place.

gibi

> 
> 
>> Cheers,
>> gibi
>> 
>> 
>>> -Sylvain
>>> 
>> 
>> 
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