[cairo] git "performance" patchset # 1 available + a few questions

[David Turner]

Hello,

the git patchset corresponding to the performance enhancements described 
on my web page[1]
is now available at:

  http://turnerdavid.neuf.fr/desktop/dturner-performance-1.patchset

sorry, it took me a long time to get it right, mainly because of lack of 
time. I have also a few
questions:

- I have some prototype code to moderately speed up the gradient 
rendering code. Before
  providing it, I'd like to understand why, in the pixman gradient code, 
a 'stopRange' field
  containing the constant value 0xFFFF is being used to deal with padding ?

  By using a constant 0x10000 for the equivalent of "stopRange", it's 
possible to get rid of
  one 64-bit division per pixel, plus some hideous modulo operations (in 
case of padding),
  and I would find this a worthy optimization. This introduces no 
distinguishible difference
  to the eye, but of course, it fails the Cairo test suite.

  Is there something I'm missing in the pixman/Cairo API that would 
prevent us from doing
  this in the current implementation ?

- on my home machine (a Pentium M latop with an Intel 855G graphics 
"card"), the "cairogears"
   benchmark indicates that the Cairo image backend is about twice 
faster than the XRender one
   (except for the TEXT2 benchmark).

  I'm a bit puzzled, but is this normal (using Ubuntu Dapper with latest 
X.Org server package) ?

  What I really want to know is wether improved performance from XRender 
is reserved to
  "dedicated" graphics cards, or if there is some way to get good 
numbers from "integrated"
  ones ?

Well, that's all for the moment,

Best Regards,

- David Turner
- The FreeType Project  (www.freetype.org)

[1] as seen on http://turnerdavid.neuf.fr/desktop/


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