Re: Snappy GUI response

On Fri, 4 Jul 2003, Alan Cox wrote:

> > Yes, scrolling long documents has finally become somewhat limited by text 
> > output performance -- and that is actually more limited by frame buffer 
> > read speed than anything else...
> 
> Its limited by the fact XFree86 doesn't know how to pull frame buffer
> data properly. On PCI/AGP you have to push data from the card. The card
> knows that, the bus knows that. XFree86 hasn't quite woken up to it.
> 

   That's not an XFree86 issue per-se.  It's a driver issue.
NVIDIA's binary drivers use DMA for GetImage and PutImage.
The fastest way to do software AA text would be to GetImage the
bounding box, render the text to the image, and PutImage it back.
Even with non-DMA GetImage and PutImage this is probably faster
that alpha blending into the framebuffer since the read-modify-
write is probably thwarting write combining.

  Actually, on a P4 which will blow it's write combine on a cache
miss, this method of drawing SW AA text is probably always faster.

			Mark.