Comment 6 for bug 1874664

Reviewed: https://review.opendev.org/723884
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=c19de075e1c6dcaeac1af25e77aa87c277fa295a
Submitter: Zuul
Branch: master

commit c19de075e1c6dcaeac1af25e77aa87c277fa295a
Author: zhangbailin <email address hidden>
Date: Tue Apr 28 20:09:00 2020 +0800

    Add nested resource providers limit for multi create

    In 21.0.0 Ussuri we were completed the nova-cyborg interaction feature,
    but there are some issue when multiple create instances.

    Creating servers with accelerators provisioned with the Cyborg service,
    if a flavor asks for resources that are provided by nested Resource
    Provider inventories (eg. VGPU) and the user wants multi-create (ie. say
    --max 2) then the scheduler could be returning a NoValidHosts exception
    even if each nested Resource Provider can support at least one specific
    instance, if the total wanted capacity is not supported by only one
    nested RP.

    For example,creating servers with accelerators provisioned with the
    Cyborg service, if two children RP have 4 VGPU inventories each:
     - you can ask for a flavor with 2 VGPU with --max 2
     - but you can't ask for a flavor with 4 VGPU and --max 2

    Related-Bug: #1874664
    Change-Id: I64647a6ba79c47c891134cedb49f03d3c61e8824