[openstack-dev] [neutron] [nova] scheduling bandwidth resources / NIC_BW_KB resource class

Moshe Levi moshele at mellanox.com
Sun Apr 10 08:07:58 UTC 2016

From: Miguel Angel Ajo Pelayo [mailto:majopela at redhat.com]
Sent: Friday, April 08, 2016 4:17 PM
To: OpenStack Development Mailing List (not for usage questions) <openstack-dev at lists.openstack.org>
Subject: [openstack-dev] [neutron] [nova] scheduling bandwidth resources / NIC_BW_KB resource class


   In the context of [1] (generic resource pools / scheduling in nova) and [2] (minimum bandwidth guarantees -egress- in neutron), I had a talk a few weeks ago with Jay Pipes,

   The idea was leveraging the generic resource pools and scheduling mechanisms defined in [1] to find the right hosts and track the total available bandwidth per host (and per host "physical network"), something in neutron (still to be defined where) would notify the new API about the total amount of "NIC_BW_KB" available on every host/physnet.
I believe that NIC bandwidth can be taken from Libvirt see [4] and the only piece that is missing is to tell nova the mapping of physnet to network interface name. (In case of SR-IOV this is already known)
I see bandwidth (speed)  as one of many capabilities of NIC, therefore I think we should take all of them in the same way in this case libvirt.  I was think of adding a new NIC as new resource to nova.

[4] - <device>
  <capability type='net'>
    <link speed='40000' state='up'/>
    <feature name='rx'/>
    <feature name='tx'/>
    <feature name='sg'/>
    <feature name='tso'/>
    <feature name='gso'/>
    <feature name='gro'/>
    <feature name='rxvlan'/>
    <feature name='txvlan'/>
    <feature name='rxhash'/>
    <feature name='rdma'/>
    <capability type='80203'/>

   That part is quite clear to me,

   From [1] I'm not sure which blueprint introduces the ability to schedule based on the resource allocation/availability itself, ("resource-providers-scheduler" seems more like an optimization to the schedule/DB interaction, right?)
My understating is that the resource provider blueprint is just a rough filter of compute nodes before passing them to the scheduler filters. The existing filters here [6] will do the  accurate filtering of resources.
see [5]

[5] - http://eavesdrop.openstack.org/irclogs/%23openstack-nova/%23openstack-nova.2016-04-04.log.html#t2016-04-04T16:24:10
[6] - http://docs.openstack.org/developer/nova/filter_scheduler.html

    And, that brings me to another point: at the moment of filtering hosts, nova  I guess, will have the neutron port information, it has to somehow identify if the port is tied to a minimum bandwidth QoS policy.

    That would require identifying that the port has a "qos_policy_id" attached to it, and then, asking neutron for the specific QoS policy  [3], then look out for a minimum bandwidth rule (still to be defined), and extract the required bandwidth from it.
I am not sure if that is the correct  way to do it, but you can create NIC bandwidth filter (or NIC capabilities filter)  and in it you can implement the way to retrieve Qos policy information by using neutron client.

   That moves, again some of the responsibility to examine and understand external resources to nova.

    Could it make sense to make that part pluggable via stevedore?, so we would provide something that takes the "resource id" (for a port in this case) and returns the requirements translated to resource classes (NIC_BW_KB in this case).

Best regards,
Miguel Ángel Ajo

[1] http://lists.openstack.org/pipermail/openstack-dev/2016-February/086371.html
[2] https://bugs.launchpad.net/neutron/+bug/1560963
[3] http://developer.openstack.org/api-ref-networking-v2-ext.html#showPolicy
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