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Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices prop
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal |
Date: |
Wed, 22 Apr 2015 18:01:56 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
* Daniel P. Berrange (address@hidden) wrote:
> On Fri, Apr 17, 2015 at 04:53:02PM +0800, Chen Fan wrote:
> > backgrond:
> > Live migration is one of the most important features of virtualization
> > technology.
> > With regard to recent virtualization techniques, performance of network I/O
> > is critical.
> > Current network I/O virtualization (e.g. Para-virtualized I/O, VMDq) has a
> > significant
> > performance gap with native network I/O. Pass-through network devices have
> > near
> > native performance, however, they have thus far prevented live migration.
> > No existing
> > methods solve the problem of live migration with pass-through devices
> > perfectly.
> >
> > There was an idea to solve the problem in website:
> > https://www.kernel.org/doc/ols/2008/ols2008v2-pages-261-267.pdf
> > Please refer to above document for detailed information.
> >
> > So I think this problem maybe could be solved by using the combination of
> > existing
> > technology. and the following steps are we considering to implement:
> >
> > - before boot VM, we anticipate to specify two NICs for creating bonding
> > device
> > (one plugged and one virtual NIC) in XML. here we can specify the NIC's
> > mac addresses
> > in XML, which could facilitate qemu-guest-agent to find the network
> > interfaces in guest.
> >
> > - when qemu-guest-agent startup in guest it would send a notification to
> > libvirt,
> > then libvirt will call the previous registered initialize callbacks. so
> > through
> > the callback functions, we can create the bonding device according to
> > the XML
> > configuration. and here we use netcf tool which can facilitate to create
> > bonding device
> > easily.
>
> I'm not really clear on why libvirt/guest agent needs to be involved in this.
> I think configuration of networking is really something that must be left to
> the guest OS admin to control. I don't think the guest agent should be trying
> to reconfigure guest networking itself, as that is inevitably going to
> conflict
> with configuration attempted by things in the guest like NetworkManager or
> systemd-networkd.
>
> IOW, if you want to do this setup where the guest is given multiple NICs
> connected
> to the same host LAN, then I think we should just let the gues admin configure
> bonding in whatever manner they decide is best for their OS install.
I disagree; there should be a way for the admin not to have to do this manually;
however it should interact well with existing management stuff.
At the simplest, something that marks the two NICs in a discoverable way
so that they can be seen that they're part of a set; with just that ID system
then an installer or setup tool can notice them and offer to put them into
a bond automatically; I'd assume it would be possible to add a rule somewhere
that said anything with the same ID would automatically be added to the bond.
However, I agree that you might be able to avoid having to do anything in the
guest agent.
Dave
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [RFC 3/3] qemu-agent: add notify for qemu-ga boot, (continued)
- [Qemu-devel] [RFC 7/7] migrate: add hostdev migrate status to support hostdev migration, Chen Fan, 2015/04/17
- Re: [Qemu-devel] [libvirt] [RFC 0/7] Live Migration with Pass-through Devices proposal, Laine Stump, 2015/04/19
- Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal, Daniel P. Berrange, 2015/04/22
- Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal, Daniel P. Berrange, 2015/04/22
- Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal, Daniel P. Berrange, 2015/04/22
- Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal, Dr. David Alan Gilbert, 2015/04/22
- Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal, Daniel P. Berrange, 2015/04/22
- Re: [Qemu-devel] [RFC 0/7] Live Migration with Pass-through Devices proposal, Dr. David Alan Gilbert, 2015/04/22
- Re: [Qemu-devel] [libvirt] [RFC 0/7] Live Migration with Pass-through Devices proposal, Laine Stump, 2015/04/23