[virt-tools-list] virt-manager over a slow link

Daniel P. Berrange berrange at redhat.com
Wed Sep 23 13:02:41 UTC 2009

On Wed, Sep 23, 2009 at 08:58:15AM -0400, Cole Robinson wrote:
> On 09/22/2009 05:28 PM, Daniel Berteaud wrote:
> > Hi everyone.
> > 
> > I'm using virt-manger 0.8 and I'm quite happy with it. I'm connecting to
> > a libvirt daemon over SSH. Everything is fine when I'm on the same local
> > network as the server. But I sometime need to use it over slower links,
> > through a VPN (~300 or 400kbps) and the VNC display is so slow that it
> > makes it very difficult to use. But when I use VNC (xvncviewer) on
> > others real hosts (vino for example) through the same VPN, a lossy
> > compression is used, and the speed is acceptable. Is there a way to use
> > lossy compression and/or reduce colore depth in order to accelerate the
> > VNC console through virt-manager (or virt-viewer) (other than manually
> > querying libvirt to find the VNC port of a VM, and open a separate SSH
> > tunnel) ?
> > 
> gtk-vnc allows this, but we don't expose the knobs in virt-manager. I'm
> all for it, just please file a feature request against upstream
> virt-manager:
> http://virt-manager.et.redhat.com/page/BugReporting
> > It'd be great to have virt-manager automatically trying different
> > encodings depending on the available BW, or to be able to manually
> > adjust the quality.
> > 
> Sounds like a good idea, not sure how it would be implemented though.

Automatic changing of quality on the fly ala tightvnc is not going 
to ever be included in gtk-vnc. The way they do is has a built-in
race condition which makes it imposible for the VNC client to know
when the server starts sending framebuffer updates with the new format.
You can see this problem by the fact that most VNC clients frequently
crash when talking to QEMU & changing colour depth.

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