RE: [RFC qemu 0/4] A PV solution for live migration optimization

From: Li, Liang Z
Date: Thu Mar 10 2016 - 02:44:39 EST

> > This patch set is the QEMU side implementation.
> >
> > The virtio-balloon is extended so that QEMU can get the free pages
> > information from the guest through virtio.
> >
> > After getting the free pages information (a bitmap), QEMU can use it
> > to filter out the guest's free pages in the ram bulk stage. This make
> > the live migration process much more efficient.
> >
> > This RFC version doesn't take the post-copy and RDMA into
> > consideration, maybe both of them can benefit from this PV solution by
> > with some extra modifications.
> I like the idea, just have to prove (review) and test it a lot to ensure we don't
> end up skipping pages that matter.
> However, there are a couple of points:
> In my opinion, the information that's exchanged between the guest and the
> host should be exchanged over a virtio-serial channel rather than virtio-
> balloon. First, there's nothing related to the balloon here.
> It just happens to be memory info. Second, I would never enable balloon in
> a guest that I want to be performance-sensitive. So even if you add this as
> part of balloon, you'll find no one is using this solution.
> Secondly, I suggest virtio-serial, because it's meant exactly to exchange free-
> flowing information between a host and a guest, and you don't need to
> extend any part of the protocol for it (hence no changes necessary to the
> spec). You can see how spice, vnc, etc., use virtio-serial to exchange data.
> Amit

Hi Amit,

Could provide more information on how to use virtio-serial to exchange data? Thread , Wiki or code are all OK.
I have not find some useful information yet.