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[Openstack] [nova] PCI alias attribute numa_policy ignored when flavor has hw:cpu_policy=dedicated set


Sean,

Thank you for the detailed explanation, i really hope if we can
backport to queens, it would be harder for me to upgrade cluster..!

On Tue, Nov 13, 2018 at 8:42 AM Sean Mooney <smooney at redhat.com> wrote:
>
> On Tue, 2018-11-13 at 07:52 -0500, Satish Patel wrote:
> > Mike,
> >
> > Here is the bug which I reported https://bugs.launchpad.net/bugs/1795920
> actully this is a releated but different bug based in the description below.
> thanks for highlighting this to me.
> >
> > Cc'ing: Sean
> >
> > Sent from my iPhone
> >
> > On Nov 12, 2018, at 8:27 AM, Satish Patel <satish.txt at gmail.com> wrote:
> >
> > > Mike,
> > >
> > > I had same issue month ago when I roll out sriov in my cloud and this is what I did to solve this issue. Set
> > > following in flavor
> > >
> > > hw:numa_nodes=2
> > >
> > > It will spread out instance vcpu across numa, yes there will be little penalty but if you tune your application
> > > according they you are good
> > >
> > > Yes this is bug I have already open ticket and I believe folks are working on it but its not simple fix. They may
> > > release new feature in coming oprnstack release.
> > >
> > > Sent from my iPhone
> > >
> > > On Nov 11, 2018, at 9:25 PM, Mike Joseph <mj at mode.net> wrote:
> > >
> > > > Hi folks,
> > > >
> > > > It appears that the numa_policy attribute of a PCI alias is ignored for flavors referencing that alias if the
> > > > flavor also has hw:cpu_policy=dedicated set.  The alias config is:
> > > >
> > > > alias = { "name": "mlx", "device_type": "type-VF", "vendor_id": "15b3", "product_id": "1004", "numa_policy":
> > > > "preferred" }
> > > >
> > > > And the flavor config is:
> > > >
> > > > {
> > > >   "OS-FLV-DISABLED:disabled": false,
> > > >   "OS-FLV-EXT-DATA:ephemeral": 0,
> > > >   "access_project_ids": null,
> > > >   "disk": 10,
> > > >   "id": "221e1bcd-2dde-48e6-bd09-820012198908",
> > > >   "name": "vm-2",
> > > >   "os-flavor-access:is_public": true,
> > > >   "properties": "hw:cpu_policy='dedicated', pci_passthrough:alias='mlx:1'",
> > > >   "ram": 8192,
> > > >   "rxtx_factor": 1.0,
> > > >   "swap": "",
> > > >   "vcpus": 2
> > > > }
> Satish in your case you were trying to use neutrons sriov vnic types such that the VF would be connected to a neutron
> network. In this case the mellanox connectx 3 virtual funcitons are being passed to the guest using the pci alias via
> the flavor which means they cannot be used to connect to neutron networks but they should be able to use affinity
> poileices.
> > > >
> > > > In short, our compute nodes have an SR-IOV Mellanox NIC (ConnectX-3) with 16 VFs configured.  We wish to expose
> > > > these VFs to VMs that schedule on the host.  However, the NIC is in NUMA region 0 which means that only half of
> > > > the compute node's CPU cores would be usable if we required VM affinity to the NIC's NUMA region.  But we don't
> > > > need that, since we are okay with cross-region access to the PCI device.
> > > >
> > > > However, we do need CPU pinning to work, in order to have efficient cache hits on our VM processes.  Therefore, we
> > > > still want to pin our vCPUs to pCPUs, even if the pins end up on on a NUMA region opposite of the NIC.  The spec
> > > > for numa_policy seem to indicate that this is exactly the intent of the option:
> > > >
> > > > https://specs.openstack.org/openstack/nova-specs/specs/queens/implemented/share-pci-between-numa-nodes.html
> > > >
> > > > But, with the above config, we still get PCI affinity scheduling errors:
> > > >
> > > > 'Insufficient compute resources: Requested instance NUMA topology together with requested PCI devices cannot fit
> > > > the given host NUMA topology.'
> > > >
> > > > This strikes me as a bug, but perhaps I am missing something here?
> yes this does infact seam like a new bug.
> can you add myself and stephen to the bug once you file it.
> in the bug please include the version of opentack you were deploying.
>
> in the interim setting hw:numa_nodes=2 will allow you to pin the guest without the error
> however the flavor and alias you have provided should have been enough.
>
> im hoping that we can fix both the alisa and neutorn based case this cycle but to do so we
> will need to reporpose original queens spec for stein and disucss if we can backport any of the
> fixes or if this would be only completed in stein+ i would hope we coudl backport fixes for the flavor
> based use case but the neutron based sue case would likely be stein+
>
> regards
> sean
> > > >
> > > > Thanks,
> > > > MJ
> > > > _______________________________________________
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