problem: reading from (rivafb) framebuffer is really slow

[Felix von Leitner]

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