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

From: Anthony Liguori
Subject: Re: [Qemu-devel] Doing a Tcl/Tk based frontend
Date: Thu, 15 Jun 2006 19:01:22 -0500
User-agent: Thunderbird (X11/20060612)

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.


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.


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