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Hi,

I have sr-iov in production in some customers with maximum number of VFs
and didn't notice any performance issues.

My understanding is that of course you will have performance penalty if you
consume all those vfs, because you're dividing the bandwidth across them,
but other than if they're are there doing nothing you won't notice anything.

But I'm just talking from my experience :)

Regards,
Pedro Sousa

On Mon, Jan 22, 2018 at 11:47 PM, Maciej Kucia <maciej at kucia.net> wrote:

> Thank you for the reply. I am interested in SR-IOV and pci whitelisting is
> certainly involved.
> I suspect that OpenStack itself can handle those numbers of devices,
> especially in telco applications where not much scheduling is being done.
> The feedback I am getting is from sysadmins who work on network
> virtualization but I think this is just a rumor without any proof.
>
> The question is if performance penalty from SR-IOV drivers or PCI itself
> is negligible. Should cloud admin configure maximum number of VFs for
> flexibility or should it be manually managed and balanced depending on
> application?
>
> Regards,
> Maciej
>
>
>>
>> 2018-01-22 18:38 GMT+01:00 Jay Pipes <jaypipes at gmail.com>:
>>
>>> On 01/22/2018 11:36 AM, Maciej Kucia wrote:
>>>
>>>> Hi!
>>>>
>>>> Is there any noticeable performance penalty when using multiple virtual
>>>> functions?
>>>>
>>>> For simplicity I am enabling all available virtual functions in my NICs.
>>>>
>>>
>>> I presume by the above you are referring to setting your
>>> pci_passthrough_whitelist on your compute nodes to whitelist all VFs on a
>>> particular PF's PCI address domain/bus?
>>>
>>> Sometimes application is using only few of them. I am using Intel and
>>>> Mellanox.
>>>>
>>>> I do not see any performance drop but I am getting feedback that this
>>>> might not be the best approach.
>>>>
>>>
>>> Who is giving you this feedback?
>>>
>>> The only issue with enabling (potentially 254 or more) VFs for each PF
>>> is that each VF will end up as a record in the pci_devices table in the
>>> Nova cell database. Multiply 254 or more times the number of PFs times the
>>> number of compute nodes in your deployment and you can get a large number
>>> of records that need to be stored. That said, the pci_devices table is well
>>> indexed and even if you had 1M or more records in the table, the access of
>>> a few hundred of those records when the resource tracker does a
>>> PciDeviceList.get_by_compute_node() [1] will still be quite fast.
>>>
>>> Best,
>>> -jay
>>>
>>> [1] https://github.com/openstack/nova/blob/stable/pike/nova/comp
>>> ute/resource_tracker.py#L572 and then
>>> https://github.com/openstack/nova/blob/stable/pike/nova/pci/
>>> manager.py#L71
>>>
>>> Any recommendations?
>>>>
>>>> Thanks,
>>>> Maciej
>>>>
>>>>
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>>>>
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>>
>>
>
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