[Spice-devel] Unfair comparisons with RDP

[John A. Sullivan III]

On Fri, 2011-07-01 at 17:05 +0200, Alon Levy wrote:
> On Fri, Jul 01, 2011 at 03:00:32PM +0200, Gianluca Cecchi wrote:
> > On Fri, Jul 1, 2011 at 1:04 PM, John A. Sullivan III  wrote:
> > > Interesting observation. That is true; we did not create separate VM
> > > definitions for SPICE and TSPlus thus the TSPlus environment is using
> > > the QXL driver.  Would we expect that to have any "supercharging" effect
> > > on RDP?
> > >
> > >
> > 
> > Probably not, because afaik (that is not so much ;-) Remote Desktop
> > (and probably tsplus too) works at the GDI call level, so it should
> > not depend so much on video adapter/video driver...
> > It was simply a question that arose analysing how to correctly
> > replicate comparisons...
> > Coming back to the test case and these operations:
> > 
> > rdp
> > 17:             display desktop, i.e., minimize all open applications
> > 42:             Paint existing LibreOffice document, i.e., restore from minimize
> > 
> > spice
> > 61:             display desktop, i.e., minimize all open applications
> > 92:             Paint existing LibreOffice document, i.e., restore from minimize
> > 
> > I think they are GDI ones, so that naturally when using rdp they are
> > executed locally on client desktop (only the gdi directives are sent),
> > while in spice (raster?) they will be network intensive (from a slow
> spice implements a driver, which implements a large part of the gdi api. So any
> operation that it doesn't implement is done via the windows gdi software rendering
> and the result given to the driver (which is spice) as an image.
> 
> So in cases where the specific operations are all implemented by the driver the
> performance should be identical. In other cases spice will be suboptimal, since
> it will send the image and not the operation. In both cases the rendering should
> be correct.
> 
> > link point of view).
> > So probably an optimized rdp could never be beaten on too slow links?
> > 
> ><snip>
Hmm . . . I remember you saying that the Windows product was actually
more developed than the Linux product.  Could it be that you have
implemented more of the GDI API than the X API (or whatever one uses for
Linux) and thus my Linux client is more regularly falling back to
sending images rather than directives?

Unfortunately, I don't have any Windows systems here in the lab to
compare with Linux. We are rousting up some Windows testers but they are
all in the UK and not here where I can observe them side by side it the
lab.  I'll have to see what I can do about that.  Just a thought - John