[Spice-devel] Unfair comparisons with RDP

[John A. Sullivan III]

On Sat, 2011-06-25 at 11:40 -0400, John A. Sullivan III wrote:
> On Sat, 2011-06-25 at 15:34 +0200, Alon Levy wrote:
> > On Fri, Jun 24, 2011 at 09:36:26PM -0400, John A. Sullivan III wrote:
> > > Hello, all. Another question to be answered only if there is time.  As
> > > we put SPICE head to head with the TSPlus implementation of RDP, SPICE
> > > seems to be coming up a bit short and I expect it is somewhat unfairly
> > > so.  It appears that RDP starts painting the screen sooner that SPICE
> > > does and so it appears more responsive even if it takes longer to finish
> > > painting the page than SPICE does.
> > > 
> > > Why is that? More importantly, is there a way to tweak SPICE to mitigate
> > > this effect or is there something in the works to make the initial delay
> > > less pronounced? Thanks - John
> > 
> > What exactly is the test? what do you mean starting / stopping, does the
> > time include the launch of spicec or spicy and the connection?
> > 
> > If it includes the connection time perhaps this is a result of the insane
> > bandwidth calculation we use, sending a very large packet of zeros at
> > connection initiation.
> <snip>
> Sorry for the lack of clarity.  I'm not referring to start up time.
> That IS noticeably slower but I think the bandwidth detection is a
> critical feature and differentiator for SPICE.
> 
> I'm referring to actual usage of the desktop.  All actions from
> scrolling a window to clicking a slider to opening a hyperlink, even
> typing very quickly seem slower to start in SPICE than in RDP. The
> difference is only a fraction of a second but it is humanly perceptible
> and gives the impression of laggard performance.
> 
> On large graphic refreshes of the screen, it seems clear that SPICE
> finishes painting the screen faster than RDP even if it appears to start
> later - it comes from behind like the Boston Red Sox (sorry for the
> American sports humor!) but appears to the user who is more concerned
> about when it starts to be slower.  When changing only small parts of
> the screen such as typing, there isn't the opportunity to "come from
> behind" and thus SPICE is being rated as slower than RDP, i.e, for
> everyday usage, not start up.  Thanks - John
<snip>
Hello, all.  I've been using both RDP via TSPlus and SPICE for over a
week now and the practical world results at least in my mode of
operation are becoming clear.  SPICE does handle major screen refreshes
better, e.g., monstrous graphics or continuously pasting a full line of
text in a full screen notepad.  Of course, SPICE is a clear winner when
it comes to video though still not practically usable on low bandwidth
links.

However, RDP is trouncing SPICE in the more common day to day tasks
involving small screen updates. For example, every time I open or switch
my screen to LibreOffice, the tool bar icons seems to pain one at a time
in SPICE where as they appear all at once in TSPlus.  Document scrolling
is more immediate and smoother.  Surprisingly, when I open the PuTTY
dialog in SPICE, it paints in sections whereas TSPlus appears all at
once.

Certainly not meant as a competition but merely as providing feedback
from practical usage.  We remain very enthusiastic about SPICE but
wonder what we can do to close the performance gap on the more common
tasks (in our usage) versus the more unusual tasks.

By the way, I did set tcp_low_latency=1 on my client to see if it made a
difference.  It subjectively appeared to but not enough to close the
gap.  I should also mention that my entire test environment is Linux
clients.  Is the Windows SPICE client noticeably faster? We are in the
process of lining up some Windows client testers.  Thanks - John