Re: [Qemu-devel] qvm86, kqemu and video speed

[James Mastros]

Struan Bartlett wrote:
> Hi,
>
> I've run some Windows 2000 performance tests on Qemu using a program 
> called PassMark PerformanceTest. You can find some results here - 
> http://www.praguespringpeople.org/Struan/Software/QEMU/Performance/2005-03-29/ 
> - I'll put more there when I make them.
>
> The results seem to me to suggest that emulated performance is weakest 
> on video operations - which doesn't surprise me if it is necessary for 
> every pixel change to be emulated - and while this won't be an issue for 
> some Qemu users it will I expect be a major issue for others.

One thing that could be done as a fairly quick hack would be to call 
SDL's bitblit function for bitblits that are simple copies.  These are 
rather common, and SDL already knows how to optimize them well -- we're 
just missing a bit of glue.  I got about halfway through doing this in a 
few hours of hacking, but realized that the video struct was completely 
undocumented, and I wasn't sure how to map from a pointer into the LFB 
back into xy coords.

After that, I think the best thing to do is to move from emulating a 
standard video card to defining our own that maps from the operations 
that the OS calls its video driver on to the operations that SDL 
implements, leaving any that do not map simply for the OS to emulate, on 
the theory that it probably knows how to better then we do.  However, 
this is a much larger undertaking, as it requires learning the driver 
model of the guest OSes.

        -=- James Mastros