[openstack-dev] [nova] [neutron] PCI pass-through network support

Ian Wells ijw.ubuntu at cack.org.uk
Fri Jan 10 23:54:46 UTC 2014

On 11 January 2014 00:04, Jiang, Yunhong <yunhong.jiang at intel.com> wrote:

>  [yjiang5] Really thanks for the summary and it is quite clear. So what’s
> the object of “equivalent devices at host level”? Because ‘equivalent
> device * to an end user *” is flavor, so is it ‘equivalent to **scheduler**”
> or ‘equivalent to **xxx**’? If equivalent to scheduler, then I’d take the
> pci_stats as a flexible group for scheduler

To the scheduler, indeed.  And with the group proposal the scheduler and
end user equivalences are one and the same.

> Secondly, for your definition of ‘whitelist’, I’m hesitate to your ‘*and*’
> because IMHO, ‘and’ means mixed two things together, otherwise, we can
> state in simply one sentence. For example, I prefer to have another
> configuration option to define the ‘put devices in the group’, or, if we
> extend it , be “define extra information like ‘group name’ for devices”.

I'm not stating what we should do, or what the definitions should mean; I'm
saying how they've been interpreted as weve discussed this in the past.
We've had issues in the past where we've had continuing difficulties in
describing anything without coming back to a 'whitelist' (generally meaning
'matching expression, as an actual 'whitelist' is implied, rather than
separately required, in a grouping system.

  Bearing in mind what you said about scheduling, and if we skip 'group'
> for a moment, then can I suggest (or possibly restate, because your
> comments are pointing in this direction):
> - we allow extra information to be added at what is now the whitelisting
> stage, that just gets carried around with the device
> [yjiang5] For ‘added at … whitelisting stage’, see my above statement
> about the configuration. However, if you do want to use whitelist, I’m ok,
> but please keep in mind that it’s two functionality combined: device you
> may assign **and** the group name for these devices.

Indeed - which is in fact what we've been proposing all along.

> - when we're turning devices into flavors, we can also match on that extra
> information if we want (which means we can tag up the devices on the
> compute node if we like, according to taste, and then bundle them up by tag
> to make flavors; or we can add Neutron specific information and ignore it
> when making flavors)
> [yjiang5] Agree. Currently we can only use vendor_id and device_id for
> flavor/alias, but we can extend it to cover such extra information since
> now it’s a API.
> - we would need to add a config param on the control host to decide which
> flags to group on when doing the stats (and they would additionally be the
> only params that would work for flavors, I think)
> [yjiang5] Agree. And this is achievable because we switch the flavor to be
> API, then we can control the flavor creation process.

OK - so if this is good then I think the question is how we could change
the 'pci_whitelist' parameter we have - which, as you say, should either
*only* do whitelisting or be renamed - to allow us to add information.
Yongli has something along those lines but it's not flexible and it
distinguishes poorly between which bits are extra information and which
bits are matching expressions (and it's still called pci_whitelist) - but
even with those criticisms it's very close to what we're talking about.
When we have that I think a lot of the rest of the arguments should simply
resolve themselves.
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