On Tue, 15 Oct 2013 12:53:00 +1030
Rusty Russell <> wrote:
> Back to the actual subject of splitting the rings: we've already removed
> the assumption that they will be contiguous from the core of the spec,
> but that does not mean transports need to do the same.
>
> The effect is to increase the ring size when large contiguous memory
> ranges can't be obtained (eg. hotplug on long-running kernels).
>
> (PAGESIZE=4096, ALIGN=4096)
>
> Contiguous Pages Max Qsz (unsplit) Max Qsz (split)
> 1 None 256
> 2 128 512
> 3 256 512
> 4 512 1024
> 5 512 1024
> 6 512 1024
> 7 1024 1024
> 8 1024 2048
>
> If this doesn't matter to you, it's almost certainly not worth the
> hassle of changing.
Well, it sounds like a good thing to have, especially since we're
likely to have both long running instances and a lot of hotplugging.
I'd like to extend the communication structure though, like I did in my
alternate proposal. I'll post a v2 without the special command reject
handling.
>
> Cheers,
> Rusty.
> PS. I note that you expose KVM_VIRTIO_CCW_RING_ALIGN through uapi: that
> seems unnecessary?
virtio-pci exposes its alignment as well.
