Re: [Qemu-devel] Doing a Tcl/Tk based frontend

[Anthony Liguori <aliguori@us.ibm.com>]

Daniel P. Berrange wrote:
>> VNC is a good idea... But isn't it a bit "laggy" for this purpose? I
>> think people accept a laggy mouse cursor in a VNC window that comes over
>> the network, but won't really accept that in virtual machine that's
>> running directly on their desktop. OTOH, I'm no VNC expert :) and maybe
>> there are tricks to speed this up?!
>>     
>
> There is no performance issue with native VNC on either localhost or
> a LAN.

That's not quite true.  I did quite a bit of benchmarking with VNC 
localhost.  I figure the best case scenario is raw encoding.  Even with 
my very optimized client, there is a slight latency and more 
importantly, a non trivial CPU overhead (~5%)

Basically, if you can't see the host cursor, you can't notice the cursor 
latency.  The CPU overhead only adds a trivial amount of time when qemu 
is CPU bound.  Certainly acceptable IMHO.

I'm 100% it's the right approach to take.

Regards,

Anthony Liguori

>  I know of places where people use a VNC session to a remote
> Linux desktop for day-to-day software development with no serious
> performance issues. Basically if your network is reasonably fast then
> there should be no issues. NB, I'm talking LAN - not WAN / Internet
> here, so assuming 100mb ethernet.
>
> That said its possible that a combination of VNC, and slow emulation
> of the display adapter within the guest OS could lower performance a
> bit more, but I'm still fairly optimistic that its usable. In any
> case slow display adapter emulation would affect the native SDL display
> mode too.
>
> Dan
>