[cairo] Redraw speed issues
ctuckey at verano.com
Wed Apr 7 13:22:51 PDT 2004
Thank you for your answers to our last set of questions. We are
continuing to explore using the OpenGL backend for our product.
I ran two instantions of the cairo-demo program on a RedHat 9 machine;
one program using the glx backend and the other using xrender. I
expected the redraw time for the glx demo to be at least as fast as the
xrender demo. However, this was not the case. The glx demo redraw was
substantially slower than the xrender demo redraw (by substantially, I
mean about 5-10 times slower). I observed substantially the same
performance with the spline and knockout demos as well.
Do you have any idea why this might be? Suggestions for further study
would be appreciated as well.
Here is some relevant information:
OS distro: Linux RedHat 9
XFree86 version: 4.3.0
xdpyinfo reports GLX as an extension
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: GeForce2 MX/AGP/SSE/3DNOW!
OpenGL version string: 1.4.1 NVIDIA 53.36
Using cairo-0.1.19-gl-r6 and libglc-0.1.0-r3
I don't if this information is of use but here is the experiment I did
and the results. I ran cairo-demo and then occluded the demo window with
another window. I uncovered the demo window, waited for it to redraw and
then repeated the process. I gathered CPU usage data as follows:
Demo program X Server
xrender 10% 81%
glx 16% 74%
An anomaly that I observed was that the glx demo CPU usage climbed to
about 75% after I quit covering and uncovering the window. It stayed
there for about 10 seconds before dropping. This didn't happen with the
Thanks for your time David.
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