problem: reading from (rivafb) framebuffer is really slow

Felix von Leitner (leitner@convergence.de)
Fri, 18 May 2001 03:29:23 +0200


When benchmarking DirectFB, I found that a typical software alpha
blending rectangle fill is completely dominated (I'm talking 90% of the
CPU cycles here) by the time it takes to read pixels from the
framebuffer.

The pixels are read linearly in chunks of aligned 32-bit words. It's a
Geforce 2 GTS in 1024x768 with 32-bit color depth using rivafb. This
looks quite crass to me. Any ideas? Maybe rivafb does not initialize
AGP and the card is in PCI mode or something?

Felix
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