Re: Performance of XPDF under Cygwin XFree86

[Adam Gundy <arg at cyberscience dot com>]

At 10:43 08/05/02 -0400, Harold L Hunt wrote:
>Adam,
>
>This is pretty much expected.  The commerical X Server on Windows that you
>mention most likely translates X graphics calls to an equivalent set of GDI
>graphics calls, which allows utilization of that $200 graphics processor you
>bought, whereas Cygwin/XFree86 currently does all drawing to an offscreen
>framebuffer that is stored in system memory with updated regions of the
>offscreen framebuffer occasionally (sometimes frequently) transferred to the
>screen.  Work is progressing on translating X graphics calls to GDI graphics
>cals in Cygwin/XFree86.  Take a look at the temporary SourceForge project
>setup to host the development:
>https://sourceforge.net/projects/xoncygwin/

that's pretty much how I thought it worked... the main reason I sent the
email was the difference between XGetImage() and XPutImage() - why is XFree86
twice as fast as XVision at putting images, but half the speed at getting them?

doesn't XGetImage() just copy straight out of your offscreen framebuffer and
send it over the network?

BTW XVision has a performance optimisation thing you can run, which tries
three different rendering methods for various X primitives - "Correct", 
"Windows"
and "Custom" - and uses the fastest for each.
It doesn't appear to test these for pixmap reading/writing.

> > I've also tries x11perf -getimage10, XFree86 achieves 590 GetImage 10x10
> > (with 100% CPU),
> > XVision 1140 (with minimal CPU) (ie XVision is almost twice as fast!)
> >
> > x11perf -putimage10, XFree86 achieves 4890 PutImage 10x10 (with 100% CPU),
> > XVision 2590 (minimal CPU) (ie XFree86 is almost twice as fast!)
> >
> > It looks like XGetImage() could do with some optimisation...



Seeya,
  Adam
--
Real Programmers don't comment their code. If it was hard to write,
it should be hard to read, and even harder to modify.
These are all my own opinions.